mulle-cc/mulle-clang-mingw ? reverse-engineered prompt

Build me this toolchain project so I can cross compile Windows programs from Linux without having to figure out all the setup myself.

I want a working build that produces the mulle clang mingw toolchain, with the usual install step into a target folder, and a clear way to run it after that. Please make sure the main build script works, and that the result can target the Windows architectures this project supports, including x86, x64, armv7, and arm64 if possible. If there are any missing dependencies or rough edges, handle them in the easiest practical way, and look up current docs online if you need to.

Also set it up so I can test it with the included example workflow, ideally by building a small app and running it with wine if I am on Linux. If Docker is the simplest way to make this reproducible, use that too and make it easy to rebuild later.