How to mark library as optional

Since upgrading to iOS 12 our iPad applications that are built with native iOS code, via Xamarin, are crashing at launch reporting they do not have access to the library CoreNFC, even though the application is not using NFC.

Termination Description: DYLD, Library not loaded: /System/Library/Frameworks/CoreNFC.framework/CoreNFC | Referenced from: 'app path' | Reason: image not found

The only answer I have found is to reference the library, but mark it as optional, does anyone know how to do that?

Thanks