Add optional tags to dalvik.

Change-Id: I29a78ccb6312d12b3ef0ed02cfbc638a5b01db9c
diff --git a/libdex/Android.mk b/libdex/Android.mk
index af33baf..558a7e5 100644
--- a/libdex/Android.mk
+++ b/libdex/Android.mk
@@ -48,6 +48,7 @@
 include $(CLEAR_VARS)
 LOCAL_SRC_FILES := $(dex_src_files)
 LOCAL_C_INCLUDES += $(dex_include_files)
+LOCAL_MODULE_TAGS := optional
 LOCAL_MODULE := libdex
 include $(BUILD_STATIC_LIBRARY)
 
@@ -62,5 +63,6 @@
 include $(CLEAR_VARS)
 LOCAL_SRC_FILES := $(dex_src_files)
 LOCAL_C_INCLUDES += $(dex_include_files)
+LOCAL_MODULE_TAGS := optional
 LOCAL_MODULE := libdex
 include $(BUILD_HOST_STATIC_LIBRARY)