Installation of ghc and ghcjs should be separate from building the codeworld-specific parts

Every time I sync with upstream, it is a hit-or-miss gamble, because half the time, the new code does not compile. The problems are always related to rebuilding ghc/ghcjs and not to the proper codeworld stuff.
I would like to stick with a version of ghc/ghcjs that I know works and keep updating only the codeworld-specific code. Alas, I cannot use the provided scripts for that. Doing "git pull" followed by running "build.sh" usually fails too.
Ideally, I think it would make sense to have two separate repostiories: one with a ghc/ghcjs version known to be working, and another with just the codeworld-specific code, which I could build without having to update ghc/ghcjs too.