[Bug libstdc++/60421] std::this_thread::sleep_for doesn't sleep for all arguments

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=60421

--- Comment #9 from Jonathan Wakely <redi at gcc dot gnu.org> ---
(In reply to Jaak Ristioja from comment #6)
> Additionally, the nanosleep code is also missing proper EINTR handling,
> which again could break the sleep.

This part is done.