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

sdk/lib/_internal/pub_generated/test/run/runs_app_in_directory_in_entrypoint_test.dart

+import 'package:path/path.dart' as path;
+import '../descriptor.dart' as d;
+import '../test_pub.dart';
+main() {
+  initConfig();
+  integration('runs a Dart application in the entrypoint package', () {
+    d.dir(
+        appPath,
+        [
+            d.appPubspec(),
+            d.dir(
+                "tool",
+                [
+                    d.file("app.dart", "main() => print('tool');"),
+                    d.dir("sub", [d.file("app.dart", "main() => print('sub');")])])]).create();
+    var pub = pubRun(args: [path.join("tool", "app")]);
+    pub.stdout.expect("tool");
+    pub.shouldExit();
+    pub = pubRun(args: [path.join("tool", "sub", "app")]);
+    pub.stdout.expect("sub");
+    pub.shouldExit();
+  });
+}