nix-env -f '<nixpkgs>' -qaP -A haskell.packages.ghc802

will run again, but the packages depending on ghc-compact will still not
build, as they have a constrain on base >= 4.10 and ghc 8.0.2 has base
4.9.1.0

Motivation for this change

Get nix-env -f '<nixpkgs>' -qaP -A haskell.packages.ghc802 running again.

Things done

• Tested using sandboxing (nix.useSandbox on NixOS, or option sandbox in nix.conf on non-NixOS)
• Built on platform(s)
  • NixOS
  • macOS
  • other Linux distributions
• Tested via one or more NixOS test(s) if existing and applicable for the change (look inside nixos/tests)
• Tested compilation of all pkgs that depend on this change using nix-shell -p nox --run "nox-review wip" nox thinks, nothing changes.
• Tested execution of all binary files (usually in ./result/bin/)
• Determined the impact on package closure size (by running nix path-info -S before and after)
• Fits CONTRIBUTING.md.