Fix pytest arguments when --save-xml is not passed (#94589)
The expression `argv + [f'--junit-xml-reruns={test_report_path}'] if TEST_SAVE_XML else []` evaluates to the empty list when `TEST_SAVE_XML` is false and would need parentheses.
Instead simplify the code by appending the argument when required directly where `test_report_path` is set.
Note that `.append()` may not be used as that would modify `argv` and in turn `UNITTEST_ARGS` which might have undesired side effects.
Without this patch `pytest.main()` would be called, i.e. no arguments which will try to discover all tests in the current working directory which ultimately leads to (many) failures.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/94589
Approved by: https://github.com/clee2000, https://github.com/Neilblaze
