Use -Werror in external/rmi4utils

* Suppress existing warnings.

Bug: 66996870
Test: build with WITH_TIDY=1
Change-Id: I2ad78f07782ca824db01e23e1309bcde34420e8e
diff --git a/Android.mk b/Android.mk
index 9df8fe7..aa2f4b5 100644
--- a/Android.mk
+++ b/Android.mk
@@ -1,2 +1,2 @@
 LOCAL_PATH := $(call my-dir)
-include $(call all-subdir-makefiles)
\ No newline at end of file
+include $(call all-subdir-makefiles)