If heap poisoning is on, pass the relevant flag to LOCAL_ASFLAGS.

This change ensures assembly files honoring heap poisoning
(notably used by stub_test) are compiled with
-DART_HEAP_POISONING=1 when this feature is turned on.

Bug: 21621105
Change-Id: I13fe456cd2733a09bdfd3a9808cfd70513b14698
diff --git a/runtime/Android.mk b/runtime/Android.mk
index b38f9bc..c1e6e09 100644
--- a/runtime/Android.mk
+++ b/runtime/Android.mk
@@ -451,6 +451,7 @@
     endif
     LOCAL_CFLAGS += $$(ART_HOST_CFLAGS)
     LOCAL_CFLAGS += -DART_DEFAULT_INSTRUCTION_SET_FEATURES="$(LIBART_HOST_DEFAULT_INSTRUCTION_SET_FEATURES)"
+    LOCAL_ASFLAGS += $$(ART_HOST_ASFLAGS)
 
     ifeq ($$(art_ndebug_or_debug),debug)
       LOCAL_CFLAGS += $$(ART_HOST_DEBUG_CFLAGS)