SITL unit tests hang forever in Debug builds

[jkflying]

To Reproduce
Steps to reproduce the behavior:

1. run make tests
2. edit build/px4_sitl_test/CMakeCache.txt to set build type from RelWithDebInfo to Debug
3. run make tests again

Expected behavior
The tests should run as per normal, but slower

What happens instead
The GTest based tests run, but the SITL tests hang until they time out

[dagar]

Let's add a SITL debug build to CI once this is resolved.

$ PX4_CMAKE_BUILD_TYPE=Debug make tests

[stale]

This issue has been automatically marked as stale because it has not had recent activity. Thank you for your contributions.