setuptools._distutils: spawn functions should match each other + add overload based on search_path param

[Avasam]

Noticed in mhammond/pywin32#2697
Upstream equivalent: pypa/distutils#390

As a reminder, here's the type restrictions for spawn:

• subprocess.check_call's first argument is typed as _CMD which is an alias for StrOrBytesPath | Sequence[StrOrBytesPath]
• if search_path=True:
  • the first element is passed to shutil.which, so cannot be a BytesPath
  • Must be mutable (re-assigning the first element)
• In some circumstances, cmd: StrOrBytesPath could work, but is not part of the intended api, and will result in incorrect error messages on failures (where the first element is what's included in the message if not in debug mode)

I'm aware that MutableSequence is invariant, but I believe that most usages of spawn will either be a string/tuple literal (which at least pyright will allow a partial union match on invariant generics, idk about mypy though). And that otherwise explicitly marking one's variable as such is easy enough: cmd: list[bytes | StrPath] = ["my", "cmd"]. This is already an issue in existing stub anyway and pypa/distutils#390 will try to address that upstream.

[srittau]

LGTM, although I would consider leaving out the unused arguments as a hint to the user that the argument probably doesn't do what they think it does. Whichever you prefer.

[Avasam]

LGTM, although I would consider leaving out the unused arguments as a hint to the user that the argument probably doesn't do what they think it does. Whichever you prefer.

I've considered doing that as well upstream. If you're also mentioning it, I think it's worth omitting the unused keyword-only arguments

[github-actions]

Diff from mypy_primer, showing the effect of this PR on open source code:

pywin32 (https://github.com/mhammond/pywin32)
+ setup.py:918: error: Unused "type: ignore" comment  [unused-ignore]