Force dx compilation target to java 6.

Because we want it to be executable on a java 6 runtime.

Change-Id: Ie6b62244b11b1b4a54b5a879cec589c66bdf3c4d
diff --git a/dx/src/Android.mk b/dx/src/Android.mk
index 4d86ac3..e53144d 100644
--- a/dx/src/Android.mk
+++ b/dx/src/Android.mk
@@ -15,6 +15,10 @@
 LOCAL_MODULE_TAGS := optional
 LOCAL_MODULE:= dx
 
+# Force java 6 target because we want java 6 runtimes to run dx, at least as long as the android SDK
+# requirement JDK 6.
+LOCAL_JAVACFLAGS:= -source 6 -target 6
+
 include $(BUILD_HOST_JAVA_LIBRARY)
 
 INTERNAL_DALVIK_MODULES += $(LOCAL_INSTALLED_MODULE)