Boostrapping Gentoo ghc package

gistfile1.txt

1) Build the Docker at https://github.com/gregwebs/ghc-docker-dev.git
   for the target arch
2) Inside the Docker, make a manual build from the upstreams ghc
   sources, with all the Debian patches applied, with a prefix of
   /tmp/ghcfoo
3) Copy /tmp/ghcfoo from the Docker to the target system
4) Set up /etc/portage/env/dev-lang/ghc to add the ghc binary in
   /tmp/ghcfoo to the path
5) Build the ebuild with USE=ghcbootstrap
6) Delete the /etc/portage/env file and rebuild the ebuild again, to
   make sure the ghc built in 5) can bootstrap itself