Add support for building with AddressSanitizer.

Change-Id: I559d21bbeb9f869f51e48ce18247ceaf766768b4
diff --git a/core/clear_vars.mk b/core/clear_vars.mk
index 41259e4..6131be7 100644
--- a/core/clear_vars.mk
+++ b/core/clear_vars.mk
@@ -119,6 +119,7 @@
 LOCAL_CTS_TEST_PACKAGE:=
 LOCAL_CTS_TEST_RUNNER:=
 LOCAL_CLANG:=
+LOCAL_ADDRESS_SANITIZER:=
 
 # Trim MAKEFILE_LIST so that $(call my-dir) doesn't need to
 # iterate over thousands of entries every time.