Use -Werror in system/vold/tests

* Comment out unused function.

Bug: 66996870
Test: build with WITH_TIDY=1
Change-Id: I7a23573af0d664a5f39f1cde3a22ac0001dac1ac
diff --git a/tests/Android.mk b/tests/Android.mk
index 8f2cda7..49da010 100644
--- a/tests/Android.mk
+++ b/tests/Android.mk
@@ -18,6 +18,7 @@
 LOCAL_MODULE := vold_tests
 LOCAL_MODULE_TAGS := eng tests
 
+LOCAL_CFLAGS := -Wall -Werror
 include $(BUILD_NATIVE_TEST)
 
 include $(CLEAR_VARS)
@@ -41,4 +42,5 @@
 LOCAL_MODULE := vold_cryptfs_scrypt_hidlization_equivalence_test
 LOCAL_MODULE_TAGS := eng tests
 
+LOCAL_CFLAGS := -Wall -Werror
 include $(BUILD_NATIVE_TEST)