FlaggedApi: enable enforcement for all non-updatable APIs

Bug: 297362755
Test: make checkapi
Change-Id: I4d384efac8a8d3b183d9b207b195ad5489db9e55
diff --git a/Android.bp b/Android.bp
index 57a5a3c..f1a3af2 100644
--- a/Android.bp
+++ b/Android.bp
@@ -621,6 +621,7 @@
     "--api-lint-ignore-prefix org. " +
     "--error NoSettingsProvider " +
     "--error UnhiddenSystemApi " +
+    "--error UnflaggedApi " +
     "--force-convert-to-warning-nullability-annotations +*:-android.*:+android.icu.*:-dalvik.* " +
     "--hide BroadcastBehavior " +
     "--hide CallbackInterface " +