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

sdk/lib/_internal/pub_generated/test/snapshot/doesnt_snapshot_an_entrypoint_dependency_test.dart

+library pub_tests;
+import 'package:path/path.dart' as p;
+import 'package:scheduled_test/scheduled_test.dart';
+import '../descriptor.dart' as d;
+import '../test_pub.dart';
+main() {
+  initConfig();
+  integration(
+      "doesn't create a snapshot for a package that depends on the " "entrypoint",
+      () {
+    servePackages((builder) {
+      builder.serve("foo", "1.2.3", deps: {
+        'bar': '1.2.3'
+      },
+          contents: [
+              d.dir("bin", [d.file("hello.dart", "void main() => print('hello!');")])]);
+      builder.serve("bar", "1.2.3", deps: {
+        'myapp': 'any'
+      });
+    });
+    d.appDir({
+      "foo": "1.2.3"
+    }).create();
+    pubGet();
+    d.nothing(p.join(appPath, '.pub', 'bin')).validate();
+  });
+}