Allow enabling RTTI in a module.

Change-Id: Ie8ce920e3ccb7e53bdf917d8ac5a386df3e7836a
diff --git a/core/definitions.mk b/core/definitions.mk
index 8fb0215..4baf31e 100644
--- a/core/definitions.mk
+++ b/core/definitions.mk
@@ -868,7 +868,7 @@
 	    $(PRIVATE_TARGET_GLOBAL_CPPFLAGS) \
 	    $(PRIVATE_ARM_CFLAGS) \
 	 ) \
-	-fno-rtti \
+	$(PRIVATE_RTTI_FLAG) \
 	$(PRIVATE_CFLAGS) \
 	$(PRIVATE_CPPFLAGS) \
 	$(PRIVATE_DEBUG_CFLAGS) \