[Bug libstdc++/93456] No overflow check in __atomic_futex_unsigned_base::_M_futex_wait_until

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93456

--- Comment #7 from Jonathan Wakely <redi at gcc dot gnu.org> ---
(In reply to CVS Commits from comment #3)
>             * testsuite/30_threads/future/members/93456.cc: ...here.

This test is failing for powerpc-darwin9, probably because I added overflow
checks for the futex version of __atomic_futex_unsigned_base but not the
generic version that uses a condition variable.