Factor out RSObjectRefCount for destructor work.

Change-Id: Ibdacc9e9f15401680bc54747664e187a05f62e25
diff --git a/Android.mk b/Android.mk
index 17c289b..8094b50 100644
--- a/Android.mk
+++ b/Android.mk
@@ -188,6 +188,7 @@
 	slang_rs_export_element.cpp	\
 	slang_rs_export_var.cpp	\
 	slang_rs_export_func.cpp	\
+	slang_rs_object_ref_count.cpp	\
 	slang_rs_reflection.cpp \
 	slang_rs_reflect_utils.cpp  \
 	slang_rs_metadata_spec_encoder.cpp