toplevel: support derivation-type updateScripts

impure.nix

@@ -143,7 +143,11 @@ let
     updateArgv = lib.optionals (pkg ? updateScript) (
       if builtins.isList pkg.updateScript then pkg.updateScript
       else if pkg.updateScript ? command then builtins.map builtins.toString pkg.updateScript.command
-      else []
+      else if (pkg.updateScript.meta or {}) ? mainProgram then
+        # raw derivation like `writeShellScriptBin`
+        [ "${lib.getExe pkg.updateScript}" ]
+      else
+        []
     );
   in {
     "${prefix}" = {