wcscmp: Work around a glibc bug. Reported by مصعب الزعبي (Mosab Al-Zoubi) <moceap@hotmail.com> in <https://lists.gnu.org/archive/html/bug-gnulib/2023-07/msg00029.html>. * m4/wcscmp.m4 (gl_FUNC_WCSCMP): Test against a glibc/arm* bug. * doc/posix-functions/wcscmp.texi: Mention the glibc/arm* bug.