Steps to debug:
* Run gazebo (or any other sim) server and client viewers via the terminal: `make posix_sitl_default gazebo_none_ide`
* In your IDE select `px4_<mode>` target you want to debug (e.g. `px4_iris`)
* Start debug session directly from IDE
This approach significantly reduces the debug cycle time because simulator (e.g. gazebo) is always running in background and you only re-run px4 process which is very light.