Fix the Mac build by working around a GCC 4.2 bug.

Ugh.

Change-Id: I352d365a9454df7d0c3c71827ece2b687e209b03
diff --git a/src/logging.h b/src/logging.h
index df6afce..7c04777 100644
--- a/src/logging.h
+++ b/src/logging.h
@@ -211,7 +211,11 @@
   const void* address_;
   size_t byte_count_;
   bool show_actual_addresses_;
+
+  // TODO: Remove the #if when Mac OS build server no longer uses GCC 4.2.*.
+#if GCC_VERSION >= 40300
   DISALLOW_COPY_AND_ASSIGN(HexDump);
+#endif
 };
 std::ostream& operator<<(std::ostream& os, const HexDump& rhs);