Why GMP doesn't support MinGW anymore?

[Andrey Khalyavin]

I'm trying to compile MinGW what is impossible without GMP. I tried to use
newest version 5.0.5. But when I try to compile gcc, compiled compiler
immediately crashes. The source of the crash is __gmpn_cpuid function in
mpn\x86_64\fat\fat_entry.asm . This function uses Linux AMD64 calling
convention instead of Windows AMD64 one needed for MinGW. Can GMP use
conditional compilation to provide a suitable version of this function?

Andrey Khalyavin.