Libhardware: Fix tests

Fix some warnings. Silence another. Less build noise.

Change-Id: Ibdbba093c2aca45343bfbe72c551b15d0f94e1b5
diff --git a/tests/hwc/Android.mk b/tests/hwc/Android.mk
index 4cae9eb..367f5f4 100644
--- a/tests/hwc/Android.mk
+++ b/tests/hwc/Android.mk
@@ -3,6 +3,7 @@
 include $(CLEAR_VARS)
 LOCAL_MODULE := libcnativewindow 
 LOCAL_SRC_FILES := cnativewindow.c util.c
+LOCAL_CFLAGS := -Wno-unused-parameter
 include $(BUILD_STATIC_LIBRARY)
 
 include $(CLEAR_VARS)