删除/Users/jiaguoshang/Desktop/WeChatAuction/ArtEnjoymentWeChatAuction/lib/UXBadgeView/LICENSE文件夹下的README.md和LICENSE文件。
删除/Users/jiaguoshang/Desktop/WeChatAuction/ArtEnjoymentWeChatAuction/lib/YXQRCodeScan文件夹下的README.md和LICENSE文件。
看到这个问题我首先问度娘，结果试了几种方法都和我的问题不一致。看来只能自立更生艰苦奋斗了。
首先我想删除/Users/jiaguoshang/Library/Developer/Xcode/DerivedData文件夹下的以ArtEnjoymentWeChatAuction-开头的文件夹及子文件夹，然后Clean Build Folder，最有运行工程，仍旧以失败告终。 
我删除/Users/jiaguoshang/Desktop/WeChatAuction/ArtEnjoymentWeChatAuction/lib/UXBadgeView和/Users/jiaguoshang/Desktop/WeChatAuction/ArtEnjoymentWeChatAuction/lib/YXQRCodeScan文件夹下的README.md文件。运行工程，发现第一条错误没有了，有门。我再删除/Users/jiaguoshang/Desktop/WeChatAuction/ArtEnjoymentWeChatAuction/lib/UXBadgeView和/Users/jiaguoshang/Desktop/WeChatAuction/ArtEnjoymentWeChatAuction/lib/YXQRCodeScan文件夹下的LICENSE文件。运行工程，没有编译错误了。问题解决了。
只所以出现这个问题是因为我从其它的项目拷贝一个公用组件到我的工程导致的。
Showing All Messages :-1: Multiple commands produce '/Users/jiaguoshang/Library/Developer/Xcode/DerivedData/ArtEnjoymentWeChatAuction-dfhwtnzqynfayrhhwndwbdbugvap/Build/Products/Debug-iphoneos/ArtEnjoymentWeChatAuction.app/README.md': 1) Target 'ArtEnjoymentWeChatAuction' (project 'ArtEnjoymentWeChatAuction') has copy command from '/Users/jiaguoshang/Desktop/WeChatAuction/ArtEnjoymentWeChatAuction/lib/UXBadgeView/README.md' to '/Users/jiaguoshang/Library/Developer/Xcode/DerivedData/ArtEnjoymentWeChatAuction-dfhwtnzqynfayrhhwndwbdbugvap/Build/Products/Debug-iphoneos/ArtEnjoymentWeChatAuction.app/README.md' 2) Target 'ArtEnjoymentWeChatAuction' (project 'ArtEnjoymentWeChatAuction') has copy command from '/Users/jiaguoshang/Desktop/WeChatAuction/ArtEnjoymentWeChatAuction/lib/YXQRCodeScan/README.md' to '/Users/jiaguoshang/Library/Developer/Xcode/DerivedData/ArtEnjoymentWeChatAuction-dfhwtnzqynfayrhhwndwbdbugvap/Build/Products/Debug-iphoneos/ArtEnjoymentWeChatAuction.app/README.md' Showing All Messages :-1: Multiple commands produce '/Users/jiaguoshang/Library/Developer/Xcode/DerivedData/ArtEnjoymentWeChatAuction-dfhwtnzqynfayrhhwndwbdbugvap/Build/Products/Debug-iphoneos/ArtEnjoymentWeChatAuction.app/LICENSE': 1) Target 'ArtEnjoymentWeChatAuction' (project 'ArtEnjoymentWeChatAuction') has copy command from '/Users/jiaguoshang/Desktop/WeChatAuction/ArtEnjoymentWeChatAuction/lib/UXBadgeView/LICENSE' to '/Users/jiaguoshang/Library/Developer/Xcode/DerivedData/ArtEnjoymentWeChatAuction-dfhwtnzqynfayrhhwndwbdbugvap/Build/Products/Debug-iphoneos/ArtEnjoymentWeChatAuction.app/LICENSE' 2) Target 'ArtEnjoymentWeChatAuction' (project 'ArtEnjoymentWeChatAuction') has copy command from '/Users/jiaguoshang/Desktop/WeChatAuction/ArtEnjoymentWeChatAuction/lib/YXQRCodeScan/LICENSE' to '/Users/jiaguoshang/Library/Developer/Xcode/DerivedData/ArtEnjoymentWeChatAuction-dfhwtnzqynfayrhhwndwbdbugvap/Build/Products/Debug-iphoneos/ArtEnjoymentWeChatAuction.app/LICENSE'
其它问题见：《升级Xcode 10后遇到的问题》。
Xcode 10.2.1 Error:Multiple commands produce问题及解决方案。
