[cfe-dev] Build clang on windows platform

[Michael Kruse via cfe-dev]

With the LLVM_DEFAULT_TARGET_TRIPLE option, you built a compiler that
cross-compiles to the target specified by default (but the compiler
itself runs on the host machine). If your want a clang.exe that runs
on the windows machine, you can either cmake+build LLVM on that
machine or use a cross-compiler (and linker) on the Ubuntu platform
(x86_64-w64-mingw32-gcc or using the clang with
LLVM_DEFAULT_TARGET_TRIPLE that you just compiled)

Michael