[PATCH 0/2] MR10577: Fix build with old clang (<13).

[Vitaly Lipatov (＠lav)]

When clang < 13 cross-compiles for Windows, it sets _MSC_VER to 1911
(< 1912). The #if/#elif chain in __config checked _MSC_VER < 1912 first,
which prevented the elif branch from defining _LIBCPP_DEFER_NEW_TO_VCRUNTIME.
This caused placement new/delete to be defined in both vcruntime_new.h and
the libc++ <new> header, resulting in redefinition errors.

Fix by checking _LIBCPP_ABI_MICROSOFT first to always define
_LIBCPP_DEFER_NEW_TO_VCRUNTIME when using vcruntime, then handle the
aligned allocation check as a nested condition.

Also add fall back to the wmemchr() call or manual loop on clang < 13.

-- 
https://gitlab.winehq.org/wine/wine/-/merge_requests/10577