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

sdk/lib/_internal/pub_generated/test/get/hosted/stay_locked_if_compatible_test.dart

+library pub_tests;
+import '../../descriptor.dart' as d;
+import '../../test_pub.dart';
+main() {
+  initConfig();
+  integration(
+      "doesn't upgrade a locked pub server package with a new "
+          "compatible constraint",
+      () {
+    servePackages((builder) => builder.serve("foo", "1.0.0"));
+    d.appDir({
+      "foo": "any"
+    }).create();
+    pubGet();
+    d.packagesDir({
+      "foo": "1.0.0"
+    }).validate();
+    servePackages((builder) => builder.serve("foo", "1.0.1"));
+    d.appDir({
+      "foo": ">=1.0.0"
+    }).create();
+    pubGet();
+    d.packagesDir({
+      "foo": "1.0.0"
+    }).validate();
+  });
+}