[Bug target/103635] size_t and uintptr_t have wrong sizes with x86_64-w64-mingw32-g++ -mabi=sysv

[mark at harmstone dot com via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103635

--- Comment #10 from Mark Harmstone <mark at harmstone dot com> ---
Created attachment 51977
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=51977&action=edit
corecrt.h

>From the file:

#ifndef _SIZE_T_DEFINED
#define _SIZE_T_DEFINED
#undef size_t
#ifdef _WIN64
__MINGW_EXTENSION typedef unsigned __int64 size_t;
#else
typedef unsigned int size_t;
#endif /* _WIN64 */
#endif /* _SIZE_T_DEFINED */

So the underlying issue is that _WIN64 is not getting set with -mabi=sysv. Is
this a bug with GCC, or in the mingw headers?