[Bug libstdc++/108225] cross build gdb error for libstdc++'s std_mutex.h on x86_64-w64-mingw32 host

[unlvsur at live dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108225

--- Comment #3 from cqwrteur <unlvsur at live dot com> ---
(In reply to cqwrteur from comment #2)
> Created attachment 54171 [details]
> Error message
> 
> This is an example of how incorrectly discarding the support of old systems
> would randomly cause build issues.
> 
> Please stop! Windows 95 support is extremely important


libstdc++ completely ignores __GTHREAD_HAS_COND macro which cause build failure
for gdb