build a ghc derivation using specific libraries in Nix

<08:43:20> "clever": ghc can never use any library you install
<08:43:30> "chessai": ah
<08:43:30> "clever": you must call ghcWithPackages, and pass it the libraries
<08:43:42> "clever": that generates a special ghc, that can only use those libraries
<08:45:34> "clever": let ghc = haskellPackages.ghcWithPackages (p: with p; [ colonnade ]);
<08:45:43> "clever": this creates a ghc derivation that is able to use colonnade
<08:46:03> "clever": cabal2nix can also take a cabal file, and generate a derivation automatically, that has every dependency