现在xcode更新不会自动安装模拟器了，需要手动安装，所以如果你使用命令行运行iOS项目时就会报错：
xcrun exited with non-zero code: 2 An error was encountered processing the command (domain=NSPOSIXErrorDomain, code=2): Unable to boot device because we cannot determine the runtime bundle. No such file or directory
打开xcode会提示simulator需要安装，点击安装模拟器即可大小：7G+
