In that case, buildEnv would say "Let's link /bin directly", which
doesn't work for this because we need to remove $out/bin/hie-wrapper and
replace it.
- Now fetching nixpgks with fetchFromGitHub by computing and saving the
sha256 at update time
- Detecting core GHC libraries and setting them to null to fix builds,
workaround for https://github.com/input-output-hk/stack2nix/issues/134
- Add override directory to fix builds for specific ghc versions
- Speed up builds by disabling library profiling for everything
- New nix file structure with powerful selection mechanisms
