hslib: Function to extract the haskell build inputs of a package.

This works by extracting out some logic from generic-builder.nix to
make it possible to get at the relevant information by overriding
mkDerivation for the haskell package.

pkgs/development/haskell-modules/make-package-set.nix

@@ -33,7 +33,7 @@ let
   inherit (haskellLib) overrideCabal;
 
   mkDerivationImpl = pkgs.callPackage ./generic-builder.nix {
-    inherit stdenv;
+    inherit stdenv haskellLib;
     inherit (pkgs) fetchurl pkgconfig glibcLocales coreutils gnugrep gnused;
     nodejs = pkgs.nodejs-slim;
     jailbreak-cabal = if (self.ghc.cross or null) != null