MT3006 Could not compute a complete dependency map for the project

I am wondering if this is a consequency of my updating to the latest Xamarin.iOS this morning... it wasn't doing this yesterday.

On the other hand I have made some other changes as well this morning.

I have a project with about 6 components. It wasn't getting very far when I went to run it, but yesterday it was at least building and deploying and running.

Now, instead, I am getting:

4 x MT3006 Could not compute a complete dependency map for the project

4 x MT3005 The dependency 'mscorlib, Version=2.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089' of the assembly (TimSort + protobuf + 2 of our own) was not found

4 x MT3001 Could not AOT the assembly (TimSort, MonoGame.Framework, 2 of our own)

I am building all these assemblies myself in Xamarin iOS projects except the TimSort.

But in any case, why has it suddenly started complaining about whatever it is now?