make new module optional

Change-Id: Iadd023fbc4f11b10d1f76c92c1cfad7ff21dde97
diff --git a/JavaLibrary.mk b/JavaLibrary.mk
index 6682a02..5600430 100644
--- a/JavaLibrary.mk
+++ b/JavaLibrary.mk
@@ -289,6 +289,7 @@
     LOCAL_BUILD_HOST_DEX := true
 
     LOCAL_MODULE := core-hostdex
+    LOCAL_MODULE_TAGS := optional
 
     include $(BUILD_HOST_JAVA_LIBRARY)