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

sdk/lib/_internal/pub_generated/test/transformer/exclusion/exclude_asset_list_test.dart

+library pub_tests;
+import '../../descriptor.dart' as d;
+import '../../test_pub.dart';
+import '../../serve/utils.dart';
+main() {
+  initConfig();
+  withBarbackVersions("any", () {
+    integration("excludes a list of assets", () {
+      d.dir(appPath, [d.pubspec({
+          "name": "myapp",
+          "transformers": [{
+              "myapp/src/transformer": {
+                "\$exclude": ["web/foo.txt", "web/sub/foo.txt"]
+              }
+            }]
+        }),
+            d.dir("lib", [d.dir("src", [d.file("transformer.dart", REWRITE_TRANSFORMER)])]),
+            d.dir(
+                "web",
+                [
+                    d.file("foo.txt", "foo"),
+                    d.file("bar.txt", "bar"),
+                    d.dir("sub", [d.file("foo.txt", "foo")])])]).create();
+      createLockFile('myapp', pkg: ['barback']);
+      pubServe();
+      requestShould404("foo.out");
+      requestShould404("sub/foo.out");
+      requestShouldSucceed("bar.out", "bar.out");
+      endPubServe();
+    });
+  });
+}