You can add support for iOS 14.5 (and watchOS 7.4) by copying the relevant DeviceSupport folders from Xcode 12.5 to Xcode 12.4.
For example the one for iOS 14.5 is located at is Xcode.app/Contents/Developer/iPhoneOS.platform/DeviceSupport/14.5
You can download the xip for Xcode 12.5 from here: https://developer.apple.com/download/more/?=xcode and extract that folder from the XCode.app inside it and move it to your installed XCode.app.
There are also publicly hosted GitHub repositories with these folders, a quick search will turn them up. It is obviously better to extract it from the official source yourself, but I think the archives are signed anyways.