Use -Werror in hardware/ril/librilutils

Bug: 66996870
Test: build with WITH_TIDY=1
Change-Id: I686a263ce0d61444cac9cba546bf5966124e0f49
diff --git a/librilutils/Android.mk b/librilutils/Android.mk
index 275fea9..62873e9 100644
--- a/librilutils/Android.mk
+++ b/librilutils/Android.mk
@@ -39,7 +39,7 @@
 LOCAL_EXPORT_C_INCLUDE_DIRS := \
     $(LOCAL_PATH)/../include
 
-LOCAL_CFLAGS : -Wall -Wextra -Werror
+LOCAL_CFLAGS := -Wall -Wextra -Werror
 
 LOCAL_PROTOC_OPTIMIZE_TYPE := nanopb-c-enable_malloc