Bogus output for gio, pango, and many other gtk related packages

The Cabal file for gio specifies a pkgconfig dependency on gio. However, that name gets re-written to glib because gio is part of glib in Nixpkgs. So we end up in a situation where there generated expression has a dependency on both the Haskell package glib in buildDepends and the system package glib in pkgconfigDepends. Since both have the same name, we cannot pass both! haskell2nix decides that the glib reference to the Haskell package set will be found automatically by callPackage and does nothing for that. For the pkgconfig reference, it generates an override to set glib = pkgs.glib. The net result is that the Haskell package reference will not be included and the build fails as reported in https://github.com/NixOS/nixpkgs/issues/5863.

Start with the Cabal file for gio and the haskell2nix handling that generates buildDepends and pkgconfigDepends, then compare the failure described in nixpkgs issue 5863. Reproduce the name collision between the Haskell glib package and the system glib package. Done means both dependencies are preserved distinctly in the generated expression and the gio build succeeds.