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

sdk/lib/_internal/pub_generated/lib/src/validator/dependency_override.dart

Index: sdk/lib/_internal/pub_generated/lib/src/validator/dependency_override.dart
diff --git a/sdk/lib/_internal/pub_generated/lib/src/validator/dependency_override.dart b/sdk/lib/_internal/pub_generated/lib/src/validator/dependency_override.dart
new file mode 100644
index 0000000000000000000000000000000000000000..c233356a7a25037ec0f71a1ccf6bce30af9112cd
--- /dev/null
+++ b/sdk/lib/_internal/pub_generated/lib/src/validator/dependency_override.dart
@@ -0,0 +1,16 @@
+library pub.validator.dependency_override;
+import 'dart:async';
+import '../entrypoint.dart';
+import '../validator.dart';
+class DependencyOverrideValidator extends Validator {
+  DependencyOverrideValidator(Entrypoint entrypoint) : super(entrypoint);
+  Future validate() {
+    if (entrypoint.root.dependencyOverrides.isNotEmpty) {
+      errors.add(
+          'Your pubspec.yaml must not have a "dependency_overrides" field.\n'
+              'This ensures you test your package against the same versions of '
+              'its dependencies\n' 'that users will have when they use it.');
+    }
+    return new Future.value();
+  }
+}