androidbp: Add LOCAL_MODULE_MAKEFILE

We're hardcoding LOCAL_PATH instead of using the my-dir macro.
LOCAL_MODULE_MAKEFILE is the other variable set up by this macro, used
to ensure that changes to the makefile rebuilds the objects defined in
the makefile.

Change-Id: I994b72ab9053d5a057eb3e35a8710038800432eb
diff --git a/androidbp/cmd/androidbp.go b/androidbp/cmd/androidbp.go
index 7889588..d990418 100644
--- a/androidbp/cmd/androidbp.go
+++ b/androidbp/cmd/androidbp.go
@@ -346,6 +346,7 @@
 	}
 
 	w.WriteString("LOCAL_PATH := " + rel + "\n")
+	w.WriteString("LOCAL_MODULE_MAKEFILE := $(lastword $(MAKEFILE_LIST))\n\n")
 	return nil
 }