[Bug libstdc++/93325] libstdc++ wrongly uses direct clock_gettime syscall on non-glibc, breaks time64

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93325

--- Comment #4 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Only fxed on master so far, but I plan to backport it.