Using alternative compiler on windows

[wmjb]

I would like to see the ability to use alternative compilers on windows, other than msvc. for example using llvm-mingw as a compiler.

[wmjb]

a temporary workaround seems to be comment out the check

distutils/distutils/ccompiler.py

Line 1086 in 49e362c

if is_mingw():

and it compiles with mingw