configure: error:
You've selected:
  BUILD:  x86_64-w64-mingw32   (the architecture we're building on)
  HOST:   x86_64-unknown-mingw32    (the architecture the compiler we're building will execute on)
  TARGET: x86_64-unknown-mingw32  (the architecture the compiler we're building will produce code for)
BUILD must equal HOST; that is, we do not support building GHC itself
with a cross-compiler.  To cross-compile GHC itself, set TARGET: stage
1 will be a cross-compiler, and stage 2 will be the cross-compiled
GHC.