Use -Werror in hardware/interfaces

* Remove unused local variables.

Bug: 66996870
Test: build with WITH_TIDY=1
Change-Id: I48dbbf670cc9eeff2391983788983420f8547cc9
diff --git a/tests/libhwbinder/aidl/Android.bp b/tests/libhwbinder/aidl/Android.bp
index a662085..6d49704 100644
--- a/tests/libhwbinder/aidl/Android.bp
+++ b/tests/libhwbinder/aidl/Android.bp
@@ -1,5 +1,6 @@
 cc_library_shared {
     name: "android.hardware.tests.libbinder",
+    defaults: ["hidl_defaults"],
 
     srcs: ["android/tests/binder/IBenchmark.aidl"],