收到iOS12.0更新推送，网上各种说更新之后手机流畅度能提升70%，那个心里激动的呀，对于iOS开发者来说，更新手机必然需要更新Xcode，要不真机都不让运行，Xcode从9.4.1更新到10.0之后开始报编译错误，下面来说说如何解决。
报错1：
:-1: Multiple commands produce '/Users/Simon/Library/Developer/Xcode/DerivedData/YueMeTV-emcpejoowcofgfdbrhckdzciyxgk/Build/Products/Debug-iphoneos/YueMeTV.app/Info.plist':
1) Target 'YueMeTV' (project 'YueMeTV') has copy command from '/Users/Simon/Desktop/公信/SmartHome_UIUE_New/Src/YueMeTV/yueme_cloud/Info.plist' to '/Users/Simon/Library/Developer/Xcode/DerivedData/YueMeTV-emcpejoowcofgfdbrhckdzciyxgk/Build/Products/Debug-iphoneos/YueMeTV.app/Info.plist'
2) Target 'YueMeTV' (project 'YueMeTV') has process command with output '/Users/Simon/Library/Developer/Xcode/DerivedData/YueMeTV-emcpejoowcofgfdbrhckdzciyxgk/Build/Products/Debug-iphoneos/YueMeTV.app/Info.plist'
文中的步骤是
Xcode->File->Project Settings->Build System->Legacy Build System.
1、InXcode, go toFile->Project/Workspace settings
2、Change thebuild systemtoLegacy Build system
报错2：
ld: warning: directory not found for option '-F/Users/Simon/Desktop/公信/SmartHome_UIUE_New/Src/YueMeTV/tools/TYLoginSDK'
ld: library not found for -lstdc++.6.0.9
clang: error: linker command failed with exit code 1 (use -v to see invocation)
解决完上述再编译报缺少
lstdc++.6.0.9库，在新xcode中发现已经去掉libstdc++.6.0.9，这就意味着项目中如果有第三方或者自己使用到lstdc++.6.0.9的地方都会报编译错误。
临时解决方案
1、 找到Xcode10之前的版本，搜索下面路劲找到libstdc++.6.0.9，
/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS.sdk/usr/lib
2、拷贝libstdc++.6.0.9到Xcode10.0对应路径下，再编译就不会报错了。
参考链接：
Xcode 10 (iOS 12) does not contain libstdc++6.0.9
关于Xcode 10.0编译不通过的问题 stdc++.6.0.9
