[Bug libstdc++/100429] threading support on windows. _GLIBCXX_HAS_GTHREADS macro is not 1 but libgcc is correct

[unlvsur at live dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100429

--- Comment #1 from cqwrteur <unlvsur at live dot com> ---
if (TlsSetValue (__key, (void*) __ptr) != 0)