有时候会在pod install的时候，有这种黄色警告。
这是在 Stack Overflow 上看到的回复。经验证有效：
I was able to fix this problem by doing the following (step by step):
Go to Build Settings
At the top select All and Combined
Under Build Options you should see Always Embed Swift Standard Libraries and it is bold.
Click on it and click delete (<-). It should now be unbolded. (Normal text = inherit)
Pod install and the error/errors should go away!
