Re-enable gdb stubtest

[srittau]

#15235 did disable stubtest for gdb, due to the following error:

Traceback (most recent call last):
  File "/tmp/stubtest-lhvl4qwb/gdb_stubtest.py", line 22, in <module>
    from mypy.stubtest import main
  File "/tmp/stubtest-lhvl4qwb/lib/python3.13/site-packages/mypy/stubtest.py", line 36, in <module>
    import mypy.build
  File "/tmp/stubtest-lhvl4qwb/lib/python3.13/site-packages/mypy/build.py", line 31, in <module>
    from librt.internal import cache_version
ModuleNotFoundError: No module named 'librt.internal'

This might be related to unsetting LD_LIBRARY_PATH in stubtest_third_party.py. In any case, we should find the error and re-enable stubtest for gdb.

[aviralgarg05]

I would like to solve this issue, please assign me this issue

[brianschubert]

I think this is happening because gdb is linked against the system interpreter, which is a Python 3.12 interpreter in the ubuntu-latest runner. Adding some debug logging shows that sys.version is 3.12.3 and sys.executable is /usr/bin/python inside the gdb script.

Right now we run stubtest under Python 3.13, so it makes sense if gdb's Python 3.12 interpreter can't import an extension module that was installed for Python 3.13.

Based on this SO question, it doesn't seem to be possible to change the Python version that gdb uses without re-compiling it. So, we'd probably need to downgrade the workflow (or at least the step running gdb stubtest) to Python 3.12 to get it working again.