Warn on overriding of hidden methods

We could prevent apps from overriding hidden methods in the same
manner they cannot override a package-private method - by creating
a separate vtable entry for the child method. For now, start by
printing a warning when a hidden method is being overridden but do
not change the semantics.

Bug: 64382372
Test: art/test.py -r -t 674-hiddenapi
Change-Id: I9d5bfa6b833a4c0f5aaffa5f82dbe9b1e1f03f1f
diff --git a/runtime/hidden_api.h b/runtime/hidden_api.h
index 7ca2378..f2ea2fd 100644
--- a/runtime/hidden_api.h
+++ b/runtime/hidden_api.h
@@ -38,6 +38,7 @@
   kReflection,
   kJNI,
   kLinking,
+  kOverride,
 };
 
 inline std::ostream& operator<<(std::ostream& os, AccessMethod value) {
@@ -51,6 +52,9 @@
     case kLinking:
       os << "linking";
       break;
+    case kOverride:
+      os << "override";
+      break;
   }
   return os;
 }