Use native async/await support in pub.

sdk/lib/_internal/pub_generated/test/get/relative_symlink_test.dart

-// Copyright (c) 2012, 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.
-
-library pub_tests;
-
-import 'dart:io';
-
-import '../descriptor.dart' as d;
-import '../test_pub.dart';
-
-main() {
-  // Pub uses NTFS junction points to create links in the packages directory.
-  // These (unlike the symlinks that are supported in Vista and later) do not
-  // support relative paths. So this test, by design, will not pass on Windows.
-  // So just skip it.
-  if (Platform.operatingSystem == "windows") return;
-
-  initConfig();
-  integration('uses a relative symlink for the self link', () {
-    d.dir(appPath, [d.appPubspec(), d.libDir('foo')]).create();
-
-    pubGet();
-
-    scheduleRename(appPath, "moved");
-
-    d.dir(
-        "moved",
-        [
-            d.dir(
-                "packages",
-                [d.dir("myapp", [d.file('foo.dart', 'main() => "foo";')])])]).validate();
-  });
-
-  integration('uses a relative symlink for secondary packages directory', () {
-    d.dir(appPath, [d.appPubspec(), d.libDir('foo'), d.dir("bin")]).create();
-
-    pubGet();
-
-    scheduleRename(appPath, "moved");
-
-    d.dir(
-        "moved",
-        [
-            d.dir(
-                "bin",
-                [
-                    d.dir(
-                        "packages",
-                        [d.dir("myapp", [d.file('foo.dart', 'main() => "foo";')])])])]).validate();
-  });
-}