[Reproducers] Fix warnings without asserts

Make sure the variable is used when asserts are compiled out.

llvm-svn: 355464

lldb/include/lldb/Utility/ReproducerInstrumentation.h

@@ -261,6 +261,7 @@ public:
   void HandleReplayResultVoid() {
     unsigned result = Deserialize<unsigned>();
     assert(result == 0);
+    (void)result;
   }
 
 private: