Full disable of C++20 time zone support

[Alexey Lapshin via Gcc-help <gcc-help@xxxxxxxxxxx>]

Hi!

I faced an issue with compiling libstdc++-v3/src/c++20/tzdb.cc:


[ERROR]    gcc/libstdc++-v3/src/c++20/tzdb.cc:110:21: error: 'constinit' variable 'std::chrono::{anonymous}::list_mutex' does not have a constant initializer
[ERROR]    gcc/libstdc++-v3/src/c++20/tzdb.cc:110:21: error: call to non-'constexpr' function 'std::mutex::mutex()'


Any plans to create a configure option to disable tzdb from build? Or at least make it compilable?

Tried --with-libstdcxx-zoneinfo=no but it does not take effect, because it does not cover line with the bug.

For now using workaround with changes in libstdc++-v3/src/c++20/Makefile*

Thanks