Fix NDEBUG builds with -Werror=unused-variable

Summary: [Fatal] Fix `NDEBUG` builds with `-Werror=unused-variable`.

Reviewed By: vitaut

Differential Revision: D20151734

fbshipit-source-id: d51fa977e5f1433ed9ab50d1c96451df8bb6630f

fatal/container/runtime_array.h

@@ -99,6 +99,7 @@ FATAL_GCC_DIAGNOSTIC_IGNORED_SHADOW_IF_BROKEN
       auto input = rhs.container_.template ref<dynamic_type>().get();
       auto end = std::copy(input, std::next(input, signed_cast(size_)), data_);
       assert(std::next(data_, signed_cast(size_)) == end);
+      (void)end;
     }
   }
 

fatal/test/random_data.h

@@ -126,6 +126,7 @@ struct random_data {
     );
 
     assert(result.size() == chunks);
+    (void)chunks;
     return result;
   }
 

fatal/test/ref_counter.h

@@ -223,6 +223,7 @@ struct ref_counter {
     guard() {
       auto duplicate = singleton().test_and_set();
       assert(!duplicate);
+      (void)duplicate;
       reset();
     }
 
@@ -407,6 +408,7 @@ struct ref_counter_guard {
   ref_counter_guard() {
     auto duplicate = singleton().test_and_set();
     assert(!duplicate);
+    (void)duplicate;
     ref_counter_reset();
   }