Revert "ghc, haskell infra: #40642 direct to master"

[peti]

Reverts #40929, because it broke ghc.

[peti]

@GrahamcOfBorg build ghc

[GrahamcOfBorg]

No attempt on aarch64-linux (full log)

The following builds were skipped because they don't evaluate on aarch64-linux: ghc

Partial log (click to expand)

a) For `nixos-rebuild` you can set
  { nixpkgs.config.allowUnsupportedSystem = true; }
in configuration.nix to override this.

b) For `nix-env`, `nix-build`, `nix-shell` or any other Nix command you can add
  { allowUnsupportedSystem = true; }
to ~/.config/nixpkgs/config.nix.

[GrahamcOfBorg]

Success on x86_64-darwin (full log)

Attempted: ghc

Partial log (click to expand)

/nix/store/g8i6m5d8h7sv52gxfn1rzws3q6zx26ja-ghc-8.2.2

[GrahamcOfBorg]

Success on x86_64-linux (full log)

Attempted: ghc

Partial log (click to expand)

these paths will be fetched (99.69 MiB download, 1305.92 MiB unpacked):
  /nix/store/3cv3s9lv79qjkqyafbclbk03gz5z813w-ghc-8.2.2
  /nix/store/zfjg0s1aacqas4j12gxy5n9bhd9fam5h-ghc-8.2.2-doc
copying path '/nix/store/zfjg0s1aacqas4j12gxy5n9bhd9fam5h-ghc-8.2.2-doc' from 'https://cache.nixos.org'...
copying path '/nix/store/3cv3s9lv79qjkqyafbclbk03gz5z813w-ghc-8.2.2' from 'https://cache.nixos.org'...
/nix/store/3cv3s9lv79qjkqyafbclbk03gz5z813w-ghc-8.2.2