static cast to int for map saver ID

nav2_map_server/src/map_saver.cpp

@@ -55,7 +55,7 @@ MapSaver::MapSaver(const rclcpp::NodeOptions & options)
   {
     mapname_ = declare_parameter("output_file_no_ext", "map");
     if (mapname_ == "map") {
-      mapname_ += "_" + std::to_string(int(now().seconds()));
+      mapname_ += "_" + std::to_string(static_cast<int>(now().seconds()));
     }
     threshold_occupied_ = declare_parameter("threshold_occupied", 65);
     if (100 < threshold_occupied_) {