Enforce overlayable API when defined

If a package defines overlayable resources, then do not allow resources
that are not defined as overlayable to be overlaid.

Bug:123600120
Test: idmap2_tests and cts-tradefed run cts -m CtsRROTestCases
Change-Id: I35120a97ccf4650e67c7ba65a60f4f3c51b0e627
diff --git a/cmds/idmap2/libidmap2/Idmap.cpp b/cmds/idmap2/libidmap2/Idmap.cpp
index 5d449e9..fa5ac8e 100644
--- a/cmds/idmap2/libidmap2/Idmap.cpp
+++ b/cmds/idmap2/libidmap2/Idmap.cpp
@@ -281,10 +281,10 @@
   if (overlayable_info == nullptr) {
     // If the resource does not have an overlayable definition, allow the resource to be overlaid.
     // Once overlayable enforcement is turned on, this check will return false.
-    return true;
+    return !target_package.DefinesOverlayable();
   }
 
-  if (!overlay_info.target_name.empty() && overlay_info.target_name != overlayable_info->name) {
+  if (overlay_info.target_name != overlayable_info->name) {
     // If the overlay supplies a target overlayable name, the resource must belong to the
     // overlayable defined with the specified name to be overlaid.
     return false;