Fix makefile

Change-Id: I8371cee8f68788329d193bb9e0da052033291c48
diff --git a/mbtk/mbtk_rild/Makefile b/mbtk/mbtk_rild/Makefile
index 453bb19..56e6534 100755
--- a/mbtk/mbtk_rild/Makefile
+++ b/mbtk/mbtk_rild/Makefile
@@ -1,5 +1,5 @@
-ROOT = $(shell pwd)/../..
-include ../Make.defines
+BUILD_ROOT = $(shell pwd)/..
+include $(BUILD_ROOT)/Make.defines
 
 LOCAL_PATH=$(BUILD_ROOT)/mbtk_rild