Use native async/await support in pub.

sdk/lib/_internal/pub_generated/test/global/binstubs/no_executables_flag_test.dart

-// Copyright (c) 2014, the Dart project authors.  Please see the AUTHORS file
-// for details. All rights reserved. Use of this source code is governed by a
-// BSD-style license that can be found in the LICENSE file.
-
-import 'package:scheduled_test/scheduled_test.dart';
-
-import '../../descriptor.dart' as d;
-import '../../test_pub.dart';
-
-main() {
-  initConfig();
-  integration("does not create binstubs if --no-executables is passed", () {
-    d.dir("foo", [d.pubspec({
-        "name": "foo",
-        "executables": {
-          "one": null
-        }
-      }),
-          d.dir("bin", [d.file("one.dart", "main() => print('ok');")])]).create();
-
-    schedulePub(args: ["global", "activate", "--source", "path", "../foo"]);
-
-    schedulePub(
-        args: ["global", "activate", "--source", "path", "../foo", "--no-executables"]);
-
-    // Should still delete old one.
-    d.dir(
-        cachePath,
-        [d.dir("bin", [d.nothing(binStubName("one"))])]).validate();
-  });
-}