Depend only on `getcwd` and `chdir` rather than attempting to also
consider the `PWD` environment variable.
There's situations where these differ, and most easily seen when running
the Python tests. Calling `pathlib.Path.cwd()` will return something
like `/home/blender/git/blender-vexp/build_asserts/tests/python` while
PWD is `/home/blender/git/blender-vexp/build_asserts`. In this case,
calling `getcwd` will match what Python shows.
Additionally, this now matches what Windows and Mac do for these
affected APIs.
Pull Request: https://projects.blender.org/blender/blender/pulls/144235
225f6c8f94