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

sdk/lib/_internal/pub_generated/test/serve/does_not_serve_gitignored_assets_test.dart

+library pub_tests;
+import '../descriptor.dart' as d;
+import '../test_pub.dart';
+import 'utils.dart';
+main() {
+  initConfig();
+  integration("doesn't serve .gitignored assets", () {
+    ensureGit();
+    d.git(
+        appPath,
+        [
+            d.appPubspec(),
+            d.dir(
+                "web",
+                [
+                    d.file("outer.txt", "outer contents"),
+                    d.dir("dir", [d.file("inner.txt", "inner contents")])]),
+            d.file(".gitignore", "/web/outer.txt\n/web/dir")]).create();
+    pubServe();
+    requestShould404("outer.txt");
+    requestShould404("dir/inner.txt");
+    endPubServe();
+  });
+}