…facts.

Remove .gitignore

Now that setuptools with mingw support is on pypi, this uncovered
the same issue as fixed in 2317473 when pip installing
MarkupSafe.

Apply the same work around here too.

By enabling customize_compiler() when using the mingw compiler class
in 2ad8784 this also enabled it for when the mingw compiler
class was used with a MSVC built CPython.

MSVC CPython doesn't have any of the config vars that are required in
customize_compiler() though. And while it would be nice if all the env
vars would be considered in that scenario too, it's not clear how this
should be implemented without any sysconfig provided fallbacks
(if CC isn't set but CFLAGS is, there is no way to pass things to
set_executables() etc.)

Given that, just restore the previous behaviour, skip customize_compiler()
with MSVC Python in all cases, and add a test.

Fixes https://github.com/pypa/setuptools/issues/4456

Deprecate distutils from the stdlib

…mpiler_msvc_python

sysconfig: skip customize_compiler() with MSVC Python again

Merge with distutils@34f9518ef