[test] Detect glibc-2.27+ and XFAIL appropriate tests

XFAIL the tests known to fail with glibc-2.27+.  This takes away
the burden of handling known failures from users, and ensures that
we will be verbosely informed when they actually start working again.

Bug report: https://bugs.llvm.org/show_bug.cgi?id=37804

Differential Revision: https://reviews.llvm.org/D56062

llvm-svn: 350717