The linker is currently broken in mono/2019-06. That is the reason the Release doesn't build for #3155 and some broken test(s) in Debug build.

So far it looks like problem with the new linker optimization, which tries to detect unreachable method bodies.

Not yet sure, whether we need to update our linker code to play nicely with it or whether it might be an upstream linker bug.

I will disable the optimization for now and leave this issue open to not forget about looking into it.