add generators and clean up directories

platforms/nix-darwin/default.nix

@@ -1,9 +0,0 @@
-{ lib, ... }:
-{
-  imports = lib.pipe (lib.filesystem.listFilesRecursive ./.) [
-    # Get only files ending in .nix
-    (builtins.filter (name: lib.hasSuffix ".nix" name))
-    # Remove this file
-    (builtins.filter (name: name != ./default.nix))
-  ];
-}