For xamarin-macios, we need the original filename used to load an assembly (because we need to look for specific resources next to that assembly).

However, the AssemblyDefinitions that we get in our custom steps don't have AssemblyDefinition.MainModule.FileName set, which complicates things. It seems like a result of this change: f5a9875

A possible solution could be to make https://github.com/mono/linker/blob/da2cc0fcd6c3a8e8e5d1b5d4a655f3653baa8980/src/linker/Linker/AssemblyResolver.cs#L88 accessible from custom steps.