Fix proguard flag file dependency.

Change-Id: Ida0f8a9b28458b1b35581b46c30b2c1cc992c42d
diff --git a/Android.mk b/Android.mk
index a536b3d..f3883ab 100644
--- a/Android.mk
+++ b/Android.mk
@@ -8,7 +8,7 @@
 LOCAL_PACKAGE_NAME := Camera
 LOCAL_SDK_VERSION := current
 
-LOCAL_PROGUARD_FLAGS := -include $(LOCAL_PATH)/proguard.flags
+LOCAL_PROGUARD_FLAG_FILES := proguard.flags
 
 include $(BUILD_PACKAGE)