Our app that uses Xamarin Forms recently started to fail its builds at the linking step for both iOS (version 7.4.0.108) and Android (4.16.0). In iOS it manifests as this error:
error MT2001: Could not link assemblies. Reason: Object reference not set to an instance of an object
and in Android this:
/Library/Frameworks/Mono.framework/External/xbuild/Xamarin/Android/Xamarin.Android.Common.targets: error : Error executing task LinkAssemblies: Object reference not set to an instance of an object
I have temporarily resolved the issue in both builds by setting the linker behavior to "Don't link", however, that is not an ideal solution as it affects the binary size for the production builds. I believe Xamarin needs to release an update to resolve this.