Error attempting to build gazebo on Ubuntu 20.10

I d/l-ed PX4-Autopilot from Github and,according to at Gazebo Simulation · PX4 Developer Guide I tried to build it. I get this error:

jon@jon-ThinkCentre-M92P:~/PX4/PX4-Autopilot$ make px4_sitl gazebo
[0/5] Performing configure step for 'sitl_gazebo'
-- install-prefix: /usr/local
-- cmake build type: RelWithDebInfo
-- Using C++17 standard
CMake Error at CMakeLists.txt:47 (find_package):
  By not providing "Findgazebo.cmake" in CMAKE_MODULE_PATH this project has
  asked CMake to find a package configuration file provided by "gazebo", but
  CMake did not find one.

  Could not find a package configuration file provided by "gazebo" with any
  of the following names:

    gazeboConfig.cmake
    gazebo-config.cmake

  Add the installation prefix of "gazebo" to CMAKE_PREFIX_PATH or set
  "gazebo_DIR" to a directory containing one of the above files.  If "gazebo"
  provides a separate development package or SDK, be sure it has been
  installed.


-- Configuring incomplete, errors occurred!
See also "/home/jon/PX4/PX4-Autopilot/build/px4_sitl_default/build_gazebo/CMakeFiles/CMakeOutput.log".
See also "/home/jon/PX4/PX4-Autopilot/build/px4_sitl_default/build_gazebo/CMakeFiles/CMakeError.log".
FAILED: external/Stamp/sitl_gazebo/sitl_gazebo-configure 
cd /home/jon/PX4/PX4-Autopilot/build/px4_sitl_default/build_gazebo && /usr/bin/cmake -DCMAKE_INSTALL_PREFIX=/usr/local -DSEND_ODOMETRY_DATA=ON -GNinja /home/jon/PX4/PX4-Autopilot/Tools/sitl_gazebo && /usr/bin/cmake -E touch /home/jon/PX4/PX4-Autopilot/build/px4_sitl_default/external/Stamp/sitl_gazebo/sitl_gazebo-configure
ninja: build stopped: subcommand failed.
make: *** [Makefile:226: px4_sitl] Error 1
jon@jon-ThinkCentre-M92P:~/PX4/PX4-Autopilot$ 

https://dev.px4.io/master/en/simulation/gazebo.html

To simplify things, I went and d/l-ed just gazebo and, according to GitHub - PX4/PX4-SITL_gazebo: Set of plugins, models and worlds to use with OSRF Gazebo Simulator in SITL and HITL., placed in its own area. Still get the same error:

jon@jon-ThinkCentre-M92P:~$ cd ~/src/sitl_gazebo/build/
jon@jon-ThinkCentre-M92P:~/src/sitl_gazebo/build$ cmake ..
-- install-prefix: /usr
-- cmake build type: RelWithDebInfo
-- Using C++17 standard
CMake Error at CMakeLists.txt:47 (find_package):
  By not providing "Findgazebo.cmake" in CMAKE_MODULE_PATH this project has
  asked CMake to find a package configuration file provided by "gazebo", but
  CMake did not find one.

  Could not find a package configuration file provided by "gazebo" with any
  of the following names:

    gazeboConfig.cmake
    gazebo-config.cmake

  Add the installation prefix of "gazebo" to CMAKE_PREFIX_PATH or set
  "gazebo_DIR" to a directory containing one of the above files.  If "gazebo"
  provides a separate development package or SDK, be sure it has been  interfaces  media    models        plugins  release-notes.html  tools  worlds
jon@jon-ThinkCentre-M92P:~/gazebo/gazebo-10.0.0$ cd cmake/

  installed.


-- Configuring incomplete, errors occurred!
See also "/home/jon/src/sitl_gazebo/CMakeFiles/CMakeOutput.log".
See also "/home/jon/src/sitl_gazebo/CMakeFiles/CMakeError.log".
jon@jon-ThinkCentre-M92P:~/src/sitl_gazebo/build$  

Any help would be greatly appreciated. I’m new here as well as new to cmake, so apologies if this is obvious.

Thanks!

Update: Installed libgazebo-dev and libopencv-dev

It got further in the build:

jon@jon-ThinkCentre-M92P:~/src/sitl_gazebo/build$ cmake ..
-- install-prefix: /usr
-- cmake build type: RelWithDebInfo
-- Using C++17 standard
-- Found Boost: /usr/lib/x86_64-linux-gnu/cmake/Boost-1.71.0/BoostConfig.cmake (found suitable version "1.71.0", minimum required is "1.58") found components: system thread filesystem 
-- Found DART: /usr/include (Required is at least version "6.6") found components: dart 
-- Found Boost: /usr/lib/x86_64-linux-gnu/cmake/Boost-1.71.0/BoostConfig.cmake (found suitable version "1.71.0", minimum required is "1.40.0") found components: thread system filesystem program_options regex iostreams date_time 
-- Looking for ignition-math6 -- found version 6.4.0
-- Searching for dependencies of ignition-math6
-- Looking for OGRE...
-- Found Ogre Ghadamon (1.9.0)
-- Looking for OGRE_Paging...
-- Found OGRE_Paging: optimized;/usr/lib/x86_64-linux-gnu/libOgrePaging.so;debug;/usr/lib/x86_64-linux-gnu/libOgrePaging.so
-- Looking for OGRE_Terrain...
-- Found OGRE_Terrain: optimized;/usr/lib/x86_64-linux-gnu/libOgreTerrain.so;debug;/usr/lib/x86_64-linux-gnu/libOgreTerrain.so
-- Looking for OGRE_Property...
-- Found OGRE_Property: optimized;/usr/lib/x86_64-linux-gnu/libOgreProperty.so;debug;/usr/lib/x86_64-linux-gnu/libOgreProperty.so
-- Looking for OGRE_RTShaderSystem...
-- Found OGRE_RTShaderSystem: optimized;/usr/lib/x86_64-linux-gnu/libOgreRTShaderSystem.so;debug;/usr/lib/x86_64-linux-gnu/libOgreRTShaderSystem.so
-- Looking for OGRE_Volume...
-- Found OGRE_Volume: optimized;/usr/lib/x86_64-linux-gnu/libOgreVolume.so;debug;/usr/lib/x86_64-linux-gnu/libOgreVolume.so
-- Looking for OGRE_Overlay...
-- Found OGRE_Overlay: optimized;/usr/lib/x86_64-linux-gnu/libOgreOverlay.so;debug;/usr/lib/x86_64-linux-gnu/libOgreOverlay.so
-- Looking for ignition-math6 -- found version 6.4.0
-- Looking for ignition-transport8 -- found version 8.0.0
-- Searching for dependencies of ignition-transport8
-- Found Protobuf: /usr/lib/x86_64-linux-gnu/libprotobuf.so;-lpthread (found suitable version "3.12.3", minimum required is "3") 
-- Config-file not installed for ZeroMQ -- checking for pkg-config
-- Checking for module 'libzmq >= 4'
--   Found libzmq , version 4.3.2
-- Checking for module 'uuid'
--   Found uuid, version 2.36.0
-- Looking for ignition-msgs5 -- found version 5.1.0
-- Searching for dependencies of ignition-msgs5
-- Looking for ignition-math6 -- found version 6.4.0
-- Checking for module 'tinyxml2'
--   Found tinyxml2, version 8.0.0
-- Looking for ignition-msgs5 -- found version 5.1.0
-- Looking for ignition-common3 -- found version 3.5.0
-- Searching for dependencies of ignition-common3
-- Looking for dlfcn.h - found
-- Looking for libdl - found
-- Searching for <ignition-common3> component [graphics]
-- Looking for ignition-common3-graphics -- found version 3.5.0
-- Searching for dependencies of ignition-common3-graphics
-- Looking for ignition-math6 -- found version 6.4.0
-- Looking for ignition-fuel_tools4 -- found version 4.1.0
-- Searching for dependencies of ignition-fuel_tools4
-- Checking for module 'jsoncpp'
--   Found jsoncpp, version 1.7.4
-- Checking for module 'yaml-0.1'
--   Found yaml-0.1, version 0.2.2
-- Checking for module 'libzip'
--   Found libzip, version 1.5.1
-- Looking for ignition-common3 -- found version 3.5.0
-- Looking for ignition-msgs5 -- found version 5.1.0
-- Checking for module 'gstreamer-1.0 >= 1.0'
--   No package 'gstreamer-1.0' found
-- Checking for module 'gstreamer-base-1.0 >= 1.0'
--   No package 'gstreamer-base-1.0' found
-- Building klt_feature_tracker without catkin
-- Building OpticalFlow with OpenCV
-- Could NOT find MAVLink (missing: MAVLINK_INCLUDE_DIRS) (found version "2.0")
-- catkin DISABLED
-- Found Protobuf: /usr/lib/x86_64-linux-gnu/libprotobuf.so;-lpthread (found version "3.12.3") 
-- Gazebo version: 11.0
-- Found GStreamer: adding gst_camera_plugin
-- Found GStreamer: adding gst_video_stream_widget
CMake Error: The following variables are used in this project, but they are set to NOTFOUND.
Please set them or make sure they are set and tested correctly in the CMake files:
GSTREAMER_LIBRARIES (ADVANCED)
    linked by target "gazebo_airship_dynamics_plugin" in directory /home/jon/src/sitl_gazebo
    linked by target "sensor_msgs" in directory /home/jon/src/sitl_gazebo
    linked by target "gazebo_airspeed_plugin" in directory /home/jon/src/sitl_gazebo
    linked by target "gazebo_groundtruth_plugin" in directory /home/jon/src/sitl_gazebo
    linked by target "physics_msgs" in directory /home/jon/src/sitl_gazebo
    linked by target "std_msgs" in directory /home/jon/src/sitl_gazebo
    linked by target "gazebo_usv_dynamics_plugin" in directory /home/jon/src/sitl_gazebo
    linked by target "gazebo_video_stream_widget" in directory /home/jon/src/sitl_gazebo
    linked by target "gazebo_gps_plugin" in directory /home/jon/src/sitl_gazebo
    linked by target "gazebo_opticalflow_mockup_plugin" in directory /home/jon/src/sitl_gazebo
    linked by target "gazebo_irlock_plugin" in directory /home/jon/src/sitl_gazebo
    linked by target "gazebo_geotagged_images_plugin" in directory /home/jon/src/sitl_gazebo
    linked by target "gazebo_parachute_plugin" in directory /home/jon/src/sitl_gazebo
    linked by target "gazebo_lidar_plugin" in directory /home/jon/src/sitl_gazebo
    linked by target "gazebo_multirotor_base_plugin" in directory /home/jon/src/sitl_gazebo
    linked by target "gazebo_wind_plugin" in directory /home/jon/src/sitl_gazebo
    linked by target "gazebo_opticalflow_plugin" in directory /home/jon/src/sitl_gazebo
    linked by target "gazebo_uuv_plugin" in directory /home/jon/src/sitl_gazebo
    linked by target "nav_msgs" in directory /home/jon/src/sitl_gazebo
    linked by target "gazebo_sonar_plugin" in directory /home/jon/src/sitl_gazebo
    linked by target "gazebo_vision_plugin" in directory /home/jon/src/sitl_gazebo
    linked by target "gazebo_gst_camera_plugin" in directory /home/jon/src/sitl_gazebo
    linked by target "mav_msgs" in directory /home/jon/src/sitl_gazebo
    linked by target "gazebo_controller_interface" in directory /home/jon/src/sitl_gazebo
    linked by target "gazebo_gimbal_controller_plugin" in directory /home/jon/src/sitl_gazebo
    linked by target "gazebo_imu_plugin" in directory /home/jon/src/sitl_gazebo
    linked by target "gazebo_mavlink_interface" in directory /home/jon/src/sitl_gazebo
    linked by target "gazebo_motor_model" in directory /home/jon/src/sitl_gazebo
    linked by target "gazebo_magnetometer_plugin" in directory /home/jon/src/sitl_gazebo
    linked by target "gazebo_barometer_plugin" in directory /home/jon/src/sitl_gazebo
    linked by target "LiftDragPlugin" in directory /home/jon/src/sitl_gazebo
    linked by target "gazebo_catapult_plugin" in directory /home/jon/src/sitl_gazebo
_MAVLINK_INCLUDE_DIR
   used as include directory in directory /home/jon/src/sitl_gazebo
   used as include directory in directory /home/jon/src/sitl_gazebo
   used as include directory in directory /home/jon/src/sitl_gazebo
   used as include directory in directory /home/jon/src/sitl_gazebo
   used as include directory in directory /home/jon/src/sitl_gazebo
   used as include directory in directory /home/jon/src/sitl_gazebo
   used as include directory in directory /home/jon/src/sitl_gazebo
   used as include directory in directory /home/jon/src/sitl_gazebo
   used as include directory in directory /home/jon/src/sitl_gazebo
   used as include directory in directory /home/jon/src/sitl_gazebo
   used as include directory in directory /home/jon/src/sitl_gazebo
   used as include directory in directory /home/jon/src/sitl_gazebo
   used as include directory in directory /home/jon/src/sitl_gazebo
   used as include directory in directory /home/jon/src/sitl_gazebo
   used as include directory in directory /home/jon/src/sitl_gazebo
   used as include directory in directory /home/jon/src/sitl_gazebo
   used as include directory in directory /home/jon/src/sitl_gazebo
   used as include directory in directory /home/jon/src/sitl_gazebo
   used as include directory in directory /home/jon/src/sitl_gazebo
   used as include directory in directory /home/jon/src/sitl_gazebo
   used as include directory in directory /home/jon/src/sitl_gazebo
   used as include directory in directory /home/jon/src/sitl_gazebo
   used as include directory in directory /home/jon/src/sitl_gazebo
   used as include directory in directory /home/jon/src/sitl_gazebo
   used as include directory in directory /home/jon/src/sitl_gazebo
   used as include directory in directory /home/jon/src/sitl_gazebo
   used as include directory in directory /home/jon/src/sitl_gazebo
   used as include directory in directory /home/jon/src/sitl_gazebo
   used as include directory in directory /home/jon/src/sitl_gazebo
   used as include directory in directory /home/jon/src/sitl_gazebo
   used as include directory in directory /home/jon/src/sitl_gazebo
   used as include directory in directory /home/jon/src/sitl_gazebo
   used as include directory in directory /home/jon/src/sitl_gazebo
   used as include directory in directory /home/jon/src/sitl_gazebo
   used as include directory in directory /home/jon/src/sitl_gazebo
   used as include directory in directory /home/jon/src/sitl_gazebo
   used as include directory in directory /home/jon/src/sitl_gazebo
   used as include directory in directory /home/jon/src/sitl_gazebo
   used as include directory in directory /home/jon/src/sitl_gazebo
   used as include directory in directory /home/jon/src/sitl_gazebo
   used as include directory in directory /home/jon/src/sitl_gazebo
   used as include directory in directory /home/jon/src/sitl_gazebo/unit_tests
   used as include directory in directory /home/jon/src/sitl_gazebo/unit_tests
   used as include directory in directory /home/jon/src/sitl_gazebo/unit_tests
   used as include directory in directory /home/jon/src/sitl_gazebo/unit_tests
   used as include directory in directory /home/jon/src/sitl_gazebo/unit_tests
   used as include directory in directory /home/jon/src/sitl_gazebo/unit_tests
   used as include directory in directory /home/jon/src/sitl_gazebo/unit_tests
   used as include directory in directory /home/jon/src/sitl_gazebo/unit_tests

-- Configuring incomplete, errors occurred!
See also "/home/jon/src/sitl_gazebo/CMakeFiles/CMakeOutput.log".
See also "/home/jon/src/sitl_gazebo/CMakeFiles/CMakeError.log".
jon@jon-ThinkCentre-M92P:~/src/sitl_gazebo/build$ cd ~/PX4/PX4-Autopilot
jon@jon-ThinkCentre-M92P:~/PX4/PX4-Autopilot$ make px4_sitl gazebo
[0/5] Performing configure step for 'sitl_gazebo'
-- install-prefix: /usr/local
-- cmake build type: RelWithDebInfo
-- Using C++17 standard
-- Found Boost: /usr/lib/x86_64-linux-gnu/cmake/Boost-1.71.0/BoostConfig.cmake (found suitable version "1.71.0", minimum required is "1.58") found components: system thread filesystem 
-- Found DART: /usr/include (Required is at least version "6.6") found components: dart 
-- Found Boost: /usr/lib/x86_64-linux-gnu/cmake/Boost-1.71.0/BoostConfig.cmake (found suitable version "1.71.0", minimum required is "1.40.0") found components: thread system filesystem program_options regex iostreams date_time 
-- Looking for ignition-math6 -- found version 6.4.0
-- Searching for dependencies of ignition-math6
-- Looking for OGRE...
-- Found Ogre Ghadamon (1.9.0)
-- Looking for OGRE_Paging...
-- Found OGRE_Paging: optimized;/usr/lib/x86_64-linux-gnu/libOgrePaging.so;debug;/usr/lib/x86_64-linux-gnu/libOgrePaging.so
-- Looking for OGRE_Terrain...
-- Found OGRE_Terrain: optimized;/usr/lib/x86_64-linux-gnu/libOgreTerrain.so;debug;/usr/lib/x86_64-linux-gnu/libOgreTerrain.so
-- Looking for OGRE_Property...
-- Found OGRE_Property: optimized;/usr/lib/x86_64-linux-gnu/libOgreProperty.so;debug;/usr/lib/x86_64-linux-gnu/libOgreProperty.so
-- Looking for OGRE_RTShaderSystem...
-- Found OGRE_RTShaderSystem: optimized;/usr/lib/x86_64-linux-gnu/libOgreRTShaderSystem.so;debug;/usr/lib/x86_64-linux-gnu/libOgreRTShaderSystem.so
-- Looking for OGRE_Volume...
-- Found OGRE_Volume: optimized;/usr/lib/x86_64-linux-gnu/libOgreVolume.so;debug;/usr/lib/x86_64-linux-gnu/libOgreVolume.so
-- Looking for OGRE_Overlay...
-- Found OGRE_Overlay: optimized;/usr/lib/x86_64-linux-gnu/libOgreOverlay.so;debug;/usr/lib/x86_64-linux-gnu/libOgreOverlay.so
-- Looking for ignition-math6 -- found version 6.4.0
-- Looking for ignition-transport8 -- found version 8.0.0
-- Searching for dependencies of ignition-transport8
-- Found Protobuf: /usr/lib/x86_64-linux-gnu/libprotobuf.so;-lpthread (found suitable version "3.12.3", minimum required is "3") 
-- Config-file not installed for ZeroMQ -- checking for pkg-config
-- Checking for module 'libzmq >= 4'
--   Found libzmq , version 4.3.2
-- Checking for module 'uuid'
--   Found uuid, version 2.36.0
-- Looking for ignition-msgs5 -- found version 5.1.0
-- Searching for dependencies of ignition-msgs5
-- Looking for ignition-math6 -- found version 6.4.0
-- Checking for module 'tinyxml2'
--   Found tinyxml2, version 8.0.0
-- Looking for ignition-msgs5 -- found version 5.1.0
-- Looking for ignition-common3 -- found version 3.5.0
-- Searching for dependencies of ignition-common3
-- Looking for dlfcn.h - found
-- Looking for libdl - found
-- Searching for <ignition-common3> component [graphics]
-- Looking for ignition-common3-graphics -- found version 3.5.0
-- Searching for dependencies of ignition-common3-graphics
-- Looking for ignition-math6 -- found version 6.4.0
-- Looking for ignition-fuel_tools4 -- found version 4.1.0
-- Searching for dependencies of ignition-fuel_tools4
-- Checking for module 'jsoncpp'
--   Found jsoncpp, version 1.7.4
-- Checking for module 'yaml-0.1'
--   Found yaml-0.1, version 0.2.2
-- Checking for module 'libzip'
--   Found libzip, version 1.5.1
-- Looking for ignition-common3 -- found version 3.5.0
-- Looking for ignition-msgs5 -- found version 5.1.0
-- Checking for module 'gstreamer-1.0 >= 1.0'
--   No package 'gstreamer-1.0' found
-- Checking for module 'gstreamer-base-1.0 >= 1.0'
--   No package 'gstreamer-base-1.0' found
-- Building klt_feature_tracker without catkin
-- Building OpticalFlow with OpenCV
-- catkin DISABLED
-- Found Protobuf: /usr/lib/x86_64-linux-gnu/libprotobuf.so;-lpthread (found version "3.12.3") 
-- Gazebo version: 11.0
-- Found GStreamer: adding gst_camera_plugin
-- Found GStreamer: adding gst_video_stream_widget
CMake Error: The following variables are used in this project, but they are set to NOTFOUND.
Please set them or make sure they are set and tested correctly in the CMake files:
GSTREAMER_LIBRARIES (ADVANCED)
    linked by target "gazebo_airship_dynamics_plugin" in directory /home/jon/PX4/PX4-Autopilot/Tools/sitl_gazebo
    linked by target "sensor_msgs" in directory /home/jon/PX4/PX4-Autopilot/Tools/sitl_gazebo
    linked by target "gazebo_airspeed_plugin" in directory /home/jon/PX4/PX4-Autopilot/Tools/sitl_gazebo
    linked by target "gazebo_groundtruth_plugin" in directory /home/jon/PX4/PX4-Autopilot/Tools/sitl_gazebo
    linked by target "physics_msgs" in directory /home/jon/PX4/PX4-Autopilot/Tools/sitl_gazebo
    linked by target "std_msgs" in directory /home/jon/PX4/PX4-Autopilot/Tools/sitl_gazebo
    linked by target "gazebo_usv_dynamics_plugin" in directory /home/jon/PX4/PX4-Autopilot/Tools/sitl_gazebo
    linked by target "gazebo_video_stream_widget" in directory /home/jon/PX4/PX4-Autopilot/Tools/sitl_gazebo
    linked by target "gazebo_gps_plugin" in directory /home/jon/PX4/PX4-Autopilot/Tools/sitl_gazebo
    linked by target "gazebo_opticalflow_mockup_plugin" in directory /home/jon/PX4/PX4-Autopilot/Tools/sitl_gazebo
    linked by target "gazebo_irlock_plugin" in directory /home/jon/PX4/PX4-Autopilot/Tools/sitl_gazebo
    linked by target "gazebo_geotagged_images_plugin" in directory /home/jon/PX4/PX4-Autopilot/Tools/sitl_gazebo
    linked by target "gazebo_parachute_plugin" in directory /home/jon/PX4/PX4-Autopilot/Tools/sitl_gazebo
    linked by target "gazebo_lidar_plugin" in directory /home/jon/PX4/PX4-Autopilot/Tools/sitl_gazebo
    linked by target "gazebo_multirotor_base_plugin" in directory /home/jon/PX4/PX4-Autopilot/Tools/sitl_gazebo
    linked by target "gazebo_wind_plugin" in directory /home/jon/PX4/PX4-Autopilot/Tools/sitl_gazebo
    linked by target "gazebo_opticalflow_plugin" in directory /home/jon/PX4/PX4-Autopilot/Tools/sitl_gazebo
    linked by target "gazebo_uuv_plugin" in directory /home/jon/PX4/PX4-Autopilot/Tools/sitl_gazebo
    linked by target "nav_msgs" in directory /home/jon/PX4/PX4-Autopilot/Tools/sitl_gazebo
    linked by target "gazebo_sonar_plugin" in directory /home/jon/PX4/PX4-Autopilot/Tools/sitl_gazebo
    linked by target "gazebo_vision_plugin" in directory /home/jon/PX4/PX4-Autopilot/Tools/sitl_gazebo
    linked by target "gazebo_gst_camera_plugin" in directory /home/jon/PX4/PX4-Autopilot/Tools/sitl_gazebo
    linked by target "mav_msgs" in directory /home/jon/PX4/PX4-Autopilot/Tools/sitl_gazebo
    linked by target "gazebo_controller_interface" in directory /home/jon/PX4/PX4-Autopilot/Tools/sitl_gazebo
    linked by target "gazebo_gimbal_controller_plugin" in directory /home/jon/PX4/PX4-Autopilot/Tools/sitl_gazebo
    linked by target "gazebo_imu_plugin" in directory /home/jon/PX4/PX4-Autopilot/Tools/sitl_gazebo
    linked by target "gazebo_mavlink_interface" in directory /home/jon/PX4/PX4-Autopilot/Tools/sitl_gazebo
    linked by target "gazebo_motor_model" in directory /home/jon/PX4/PX4-Autopilot/Tools/sitl_gazebo
    linked by target "gazebo_magnetometer_plugin" in directory /home/jon/PX4/PX4-Autopilot/Tools/sitl_gazebo
    linked by target "gazebo_barometer_plugin" in directory /home/jon/PX4/PX4-Autopilot/Tools/sitl_gazebo
    linked by target "LiftDragPlugin" in directory /home/jon/PX4/PX4-Autopilot/Tools/sitl_gazebo
    linked by target "gazebo_catapult_plugin" in directory /home/jon/PX4/PX4-Autopilot/Tools/sitl_gazebo

-- Configuring incomplete, errors occurred!
See also "/home/jon/PX4/PX4-Autopilot/build/px4_sitl_default/build_gazebo/CMakeFiles/CMakeOutput.log".
See also "/home/jon/PX4/PX4-Autopilot/build/px4_sitl_default/build_gazebo/CMakeFiles/CMakeError.log".
FAILED: external/Stamp/sitl_gazebo/sitl_gazebo-configure 
cd /home/jon/PX4/PX4-Autopilot/build/px4_sitl_default/build_gazebo && /usr/bin/cmake -DCMAKE_INSTALL_PREFIX=/usr/local -DSEND_ODOMETRY_DATA=ON -GNinja /home/jon/PX4/PX4-Autopilot/Tools/sitl_gazebo && /usr/bin/cmake -E touch /home/jon/PX4/PX4-Autopilot/build/px4_sitl_default/external/Stamp/sitl_gazebo/sitl_gazebo-configure
ninja: build stopped: subcommand failed.
make: *** [Makefile:226: px4_sitl] Error 1
jon@jon-ThinkCentre-M92P:~/PX4/PX4-Autopilot$ 

The hunt continues…

Hi, for the same error, in my case,
after libgazebo9-dev installed by sudo apt install libgazebo9-dev command, it disappeared.

See px4 cmake error with gazebo · Issue #5393 · PX4/PX4-Autopilot · GitHub

The problem here is very specific to installing Gazebo, have you tried the instructions on the Gazebo website?

http://gazebosim.org/tutorials?tut=install_ubuntu&cat=install