[Bug c++/109688] SPDLOG build fails with C++20 and -DSPDLOG_USE_STD_FORMAT=1

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=109688

--- Comment #9 from Jonathan Wakely <redi at gcc dot gnu.org> ---
That fixed the fmt::formatter::format function, and this fixed the
std::formatter::format function:
https://github.com/gabime/spdlog/commit/3cd06a3d40cd9054cbc997fe6e28c5a472b93b8c