Is there a guide or script to build ghc from source (not the prebuilt binary)?

At MacPorts we’re running into issues on macOS Catalina 10.15 with the bootstrapped-from-prebuilt ghc. See https://trac.macports.org/ticket/59467 .

It would preferable and probably more robust to be able to bootstrap everything from source, and highly preferable to be able to do this with a clang compiler of choice.