meson: Don't check for posix_memalign on windows

There's a mingw bug for this, it exports __builtin_posix_memalign but
not posix_memalign, so the check will succeed, but compiling will fail.

Reviewed-by: Eric Engestrom <eric.engestrom@intel.com>
Acked-by: Kristian H. Kristensen <hoegsberg@google.com>
1 file changed