CPython fails to build on MSVC with latest C standard flag

[Fidget-Spinner]

Bug report

Bug description:

When passing /std:clatest to MSVC, the current CPython fails to build.

CPython versions tested on:

CPython main branch

Operating systems tested on:

No response

Linked PRs

• gh-135927: Fix MSVC Clatest C builds #135935
• gh-135927: Check _MSC_VER to define _Py_NULL macro #135987

[zooba]

For the record, I don't like building with Clatest and if we're considering making that change upstream, we should pick a version. If we rely on those features being there, specifying a version will cause people's builds to fail with a useful error message, rather than whatever vague error they get for invalid syntax.

We have to assume that people build CPython from source, and have to assume they aren't doing it on our build machines, so let's be as inclusive as we can of different environments.

[Fidget-Spinner]

For the record, I don't like building with Clatest and if we're considering making that change upstream, we should pick a version. If we rely on those features being there, specifying a version will cause people's builds to fail with a useful error message, rather than whatever vague error they get for invalid syntax.

We have to assume that people build CPython from source, and have to assume they aren't doing it on our build machines, so let's be as inclusive as we can of different environments.

I'm not yet pushing to build with Clatest upstream. FWIW, I just filed the bug because I tried building with Clatest locally and it failed. If any features don't work on C11, they will be guarded with the usual ifdefs. This follows Python's C standard policy after all.