如何在Xcode中的运行脚本构建阶段中使用Swift标志？

I added "-D MYOWNFLAG" to Other Swift Flags in Build Settings of Xcode. Now, in my Run Script found in Build Phases, I want to check for the existence of the flag "MYOWNFLAG" and execute something (e.g. change Info.plist setting value) if it exists. in