The latest version of iOS (13.4) was recently released, and with it the new version of Xcode. This new version of Xcode only runs on macOS Catalina. If, like me, you have been avoiding Catalina as much as possible this is a problem, because if you try to use the last version of Xcode that supports Mojave (Xcode 11.3) to Build and Run on a device that is running iOS 13.4 it will give you an error (as it only has support for iOS versions up to iOS 13.3).
However, you can add extra iOS version support to Xcode by taking the DeviceSupport files from one version and adding them to another version (both to add support for newer, and older versions of iOS).
- Find or download a version of Xcode that support the iOS version you want, in this case the latest one.
- Extract the Xcode.app bundle, navigate to
- Take the folder for the iOS version you need and place it in the equivalent directory inside the version of Xcode you are running.
- At this point you'll need to restart Xcode at the minimum, though in my case I had to reboot completely.
- Now connect the iOS device running that iOS version and attempt to Build and Run to it.
- Xcode should not pull down the symbol files it needs from the device and you are good to go.
This will not give you the new SDK, but should allow you to continue using your existing Xcode for a while longer.