remove extraLib, replace mkScript with writeShellApplication

overlays/lib.nix

@@ -1,16 +0,0 @@
-_final: prev: {
-  extraLib = prev.lib // {
-
-    # Quickly package shell scripts with their dependencies
-    # From https://discourse.nixos.org/t/how-to-create-a-script-with-dependencies/7970/6
-    mkScript = { name, file, env ? [ ] }:
-      prev.pkgs.writeScriptBin name ''
-        for i in ${prev.lib.concatStringsSep " " env}; do
-          export PATH="$i/bin:$PATH"
-        done
-
-        exec ${prev.pkgs.bash}/bin/bash ${file} $@
-      '';
-  };
-
-}