升級xcode10.3後打包問題。

SDK Version Issue. This app was built with the iOS 12.0 SDK. All iOS apps submitted to the App Store must be built with the iOS 11 SDK or later, included in Xcode 9 or later. Further, starting March 2019, all iOS apps submitted to the App Store must be built with the iOS 12.1 SDK or later, included in Xcode 10.1 or later.

解決辦法：

/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDK，刪除iPhoneOS12.0.sdk