[Bug libstdc++/99832] std::chrono::system_clock::to_time_t needs ABI tag for 32-bit time_t

[redi at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99832

--- Comment #18 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Done on trunk, but this seems worth backporting because _TIME_BITS=64 has been
a thing for some time already.