[Bug d/91600] "Architecture not supported" reported for MinGW-W64

[ibuclaw at gdcproject dot org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91600

--- Comment #1 from Iain Buclaw <ibuclaw at gdcproject dot org> ---
The following versions may be defined by the compiler on mingw targets

Windows
MinGW
Win32
Win64

And on cygwin targets.

Windows
Cygwin
Posix

Druntime should compile fine if these exist.