How to build a new version of ghc

[kencu]

Up to ghc-9.4.4, I use:

1. a previous version of ghc as the bootstrap compiler. Usually the ghc two versions earlier is used to bootstrap, and for ghc 9.4.4, bootstrapping with ghc 9.0.x is the last one that works using the traditional makefile build of ghc.
2. the ghc source tarballs
3. a macports installation of a recent version of clang, ld64, and cctools
4. the alex, happy, and hscolour binaries

and then a script from ghc upstream, modified to use macports instead of homebrew for the toolchain parts, and modified to not try to upload the final product back up to ghc. I will upload this script separately.

building the documentation using sphinx and latex and texlive is always a troublesome step. I did it for most of the ghc installer xz files up in this repo, but for the last two, ghc 9.2.x and ghc 9.4.x, I disabled the documentation as it just wasn't building.

Several small patches are required to the ghc source to replace missing functions like strnlen not found on 10.6. These appear benign in nature. The patches are slightly different from ghc version to ghc version as the source changes a bit.