Ever since I've upgraded to Xcode 9, I've been getting the error from the Xib compiler: Unsupported Configuration: "This file is set to build for a version older than the deployment target." And I know I'm not the only one.
I did specify my files to use the deployment target of 11.2. And I did check the source code of my .xib and can't even find anything that seems to specify the target at all. Anywhere else that the required version might be specified?
Confirm your process. Select that XIB, then use the 'File Inspector' on the right - look under 'Interface Builder Document' - set 'Opens In' (if not done for you), to Latest Xcode (9.0), then 'Builds For' to the nearest iOS to what you expect your app to minimally support...11.2 in your example.
Do this manually for each one that throws that error, option-clean the build folder, and you should be good to go. Still no joy, drop 'Builds For' to something lower, such as 11.0, option-clean again and check for errors. Still no joy, do you have multiple targets in that project?