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

sdk/lib/_internal/pub_generated/test/dart2js/reports_dart_parse_errors_test.dart

+import 'package:path/path.dart' as p;
+import 'package:scheduled_test/scheduled_test.dart';
+import 'package:scheduled_test/scheduled_stream.dart';
+import '../../lib/src/exit_codes.dart' as exit_codes;
+import '../descriptor.dart' as d;
+import '../test_pub.dart';
+main() {
+  initConfig();
+  integration("reports Dart parse errors", () {
+    currentSchedule.timeout *= 3;
+    d.dir(
+        appPath,
+        [
+            d.appPubspec(),
+            d.dir(
+                'web',
+                [
+                    d.file('file.txt', 'contents'),
+                    d.file('file.dart', 'void void;'),
+                    d.dir('subdir', [d.file('subfile.dart', 'void void;')])])]).create();
+    var pub = startPub(args: ["build"]);
+    pub.stdout.expect(startsWith("Loading source assets..."));
+    pub.stdout.expect(startsWith("Building myapp..."));
+    var consumeFile = consumeThrough(
+        inOrder(
+            ["[Error from Dart2JS]:", startsWith(p.join("web", "file.dart") + ":")]));
+    var consumeSubfile = consumeThrough(
+        inOrder(
+            [
+                "[Error from Dart2JS]:",
+                startsWith(p.join("web", "subdir", "subfile.dart") + ":")]));
+    pub.stderr.expect(
+        either(
+            inOrder([consumeFile, consumeSubfile]),
+            inOrder([consumeSubfile, consumeFile])));
+    pub.shouldExit(exit_codes.DATA);
+    d.dir(appPath, [d.dir('build', [d.nothing('web')])]).validate();
+  });
+}