[Bug libstdc++/110739] std::format for chrono types compiles very slowly

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110739

--- Comment #3 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Explicit instantiation declarations+definitions might help, both in <chrono>
and <format>.