libsysutil: turn on -Werror (part deux)

- x86_64 format warnings

Change-Id: I81c2702f564bcada946f6a10f34bbf34c90f766b
diff --git a/libsysutils/Android.mk b/libsysutils/Android.mk
index 1451b0d..246f954 100644
--- a/libsysutils/Android.mk
+++ b/libsysutils/Android.mk
@@ -18,7 +18,7 @@
 
 LOCAL_C_INCLUDES :=
 
-LOCAL_CFLAGS :=
+LOCAL_CFLAGS := -Werror
 
 LOCAL_SHARED_LIBRARIES := libcutils liblog