nix fix for Prelude.hs-in-top-level issue

  overrides = self: super: {
    category = obelisk.nixpkgs.haskell.lib.overrideSrc super.category {
      src = obelisk.nixpkgs.runCommand "fixed-category-source" {} ''
        mkdir $out
        cd $out
        tar -xf ${super.category.src} --strip-components 1
        mkdir $out/src
        mv $out/{Control,Data,Prelude.hs} $out/src/
        sed -i 's/library/library\n  hs-source-dirs: src/' $out/category.cabal
      '';
    };
  };