This allows picking up on mingw triples that often use 'w64' instead
of 'pc' as the vendor part.
Differential Revision: https://reviews.llvm.org/D111297
This allows testing the rest of those headers on most platforms, instead
of XFAILing the whole test just because of a few functions.
As a fly-by fix, remove std/utilities/time/date.time/ctime.pass.cpp,
which was a duplicate of std/language.support/support.runtime/ctime.pass.cpp.
Differential Revision: https://reviews.llvm.org/D108295