Clang pretends to be gcc 4.4 and that causes some re-definition errors.
The problem has been reported to the upstream some time ago but nothing
was done about it.
It was using __GNUC__ < 8 to check if _xgetbv intrinsic is available.
Since we always use zig cc with this header, we know we have clang 9,
which does have this intrinsic.
also start prefering NtDll API. so far:
* NtQueryInformationFile
* NtClose
adds a performance workaround for windows unicode conversion. but that
should probably be removed before merging
