Add make rule for dex.

Change-Id: I2807095462667f6d2b3723b315d5365c77a60931
diff --git a/JavaLibrary.mk b/JavaLibrary.mk
index 8cf31d4..5bdfb01 100644
--- a/JavaLibrary.mk
+++ b/JavaLibrary.mk
@@ -157,6 +157,12 @@
 # Build for the host.
 #
 
+include $(CLEAR_VARS)
+LOCAL_SRC_FILES := $(call all-main-java-files-under, dex)
+LOCAL_MODULE_TAGS := optional
+LOCAL_MODULE := dex-host
+include $(BUILD_HOST_JAVA_LIBRARY)
+
 ifeq ($(WITH_HOST_DALVIK),true)
 
     # Definitions to make the core library.