Store the async-await compiled pub code directly in the repo.

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

+library pub_tests;
+import 'dart:io';
+import '../descriptor.dart' as d;
+import '../test_pub.dart';
+main() {
+  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();
+  });
+}