Hacking on GHC for the first time is death by a thousand cuts.
Any one part of the process is not that bad, but as a whole the process is very cumbersome for someone new.
With the docker image, would it be possible to distribute pre-built versions of the GHC source tarball? Maybe phabricator could do this? The biggest overhead for me always is that compiling the source the first time takes something like 2 hours (even without optimizations) on my machine. If there was a pre-built version, I could just change one file and only recompile what I changed.