Getting error while creating new work_item in PX4 Autopilot

I copied “PX4-Autopilot/src/examples/work_item” folder, and made changes in all 4 files CMakeLists.txt, Kconfig, .hpp and .cpp files accordingly.
Also added “CONFIG_EXAMPLES_WORK_ITEM_TEST=y” in PX4-Autopilot/boardconfig and in PX4-Autopilot/boards/px4/sitl/default.px4board.
Then executed cmake, and make commands.
When I try to execute “make px4_sitl gz_x500”, I am getting error as:
make: *** No rule to make target ‘px4_sitl’. Stop.
Why I am not able to execute px4_sitl ?
Please suggest.

Did you first go through the toolchain installation? make sure you also synced the submodules

I am able to execute my work item (by executing server - bin/px4 beforehand) successfully.
I am on Ubuntu 22.04 LTS.
While executing PX4-Autopilot/Tools/setup/ubuntu.sh getting error as:
Err:8 Index of /team-gcc-arm-embedded/ppa/ubuntu jammy Release
404 Not Found [IP: 185.125.190.80 443]

And I am not able to fix it, any suggestions ?