[UE4]解决UE4打包错误 “is being used by another process”

引擎版本：4.14.3
打包错误信息：
UATHelper: Packaging (Windows (64-bit)): Program.Main: ERROR: AutomationTool terminated with exception: System.IO.IOException: The process cannot access the file ‘C:\YourPath\WindowsNoEditor\Engine\Extras\Redist\en-us\UE4PrereqSetup_x64.exe’ because it is being used by another process.

产生此错误的原因是EpicGamesLauncher进程，正常情况下登录器就算是打开，也不会导致打包失败，有可能是我使用源码版被我修改的有问题了。

把EpicGamesLauncher进程关闭就可以正常打包了。