bpo-37421: Fix test_distutils.test_build_ext() (GH-14564)


test_distutils.test_build_ext() is now able to remove the temporary
directory on Windows: don't import the newly built C extension ("xx")
in the current process, but test it in a separated process.
(cherry picked from commit 74c9dd57771f4f061ee83b069c8e7b37de41246b)

Co-authored-by: Victor Stinner <vstinner@redhat.com>
3 files changed