[Bug libstdc++/120187] Inclusion of ciso646 incorrectly points to using version in C++17 mode

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

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=120187

--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Using -Werror -Wno-error=deprecated should solve your problem.

Abseil should probably be using __has_include(<version>) instead of depending
on C++17 vs C++20.