When "make posix gazebo_rover" it report "error: '/Firmware/Tools/sitl_gazebo/protobuf::protoc' missing and no known rule to make it "

#1

When “make posix gazebo_rover” it report "error: ‘/Firmware/Tools/sitl_gazebo/protobuf::protoc’ missing and no known rule to make it
" as follow.
How can I fix it?

Gazebo version: 7.12
– Checking for module ‘eigen3’
– Found eigen3, version 3.2.0
– Configuring done
– Generating done
– Build files have been written to: /home/ubuntu/shelley/Firmware/build/px4_sitl_default/build_gazebo
[47/50] Performing build step for ‘sitl_gazebo’
FAILED: cd /home/ubuntu/shelley/Firmware/build/px4_sitl_default/build_gazebo && /usr/local/bin/cmake --build . && /usr/local/bin/cmake -E touch /home/ubuntu/shelley/Firmware/build/px4_sitl_default/external/Stamp/sitl_gazebo/sitl_gazebo-build
ninja: error: ‘/home/ubuntu/shelley/Firmware/Tools/sitl_gazebo/protobuf::protoc’, needed by ‘CommandMotorSpeed.pb.cc’, missing and no known rule to make it
[47/50] Linking CXX executable bin/px4
ninja: build stopped: subcommand failed.
make: *** [px4_sitl_default] Error 1

#2

sudo apt-get install protobuf-compiler