Add support for Windows host and targets, ARM64 and x86_64#642

ArchangelX360 wants to merge 25 commits into

bazel-contrib:masterbazel-contrib/toolchains_llvm:masterfrom

ArchangelX360:archangelx360/llvm_windows_host_targetArchangelX360/toolchains_llvm:archangelx360/llvm_windows_host_targetCopy head branch name to clipboard