This is a simple regression from Loom added code. In `JVM_handle_linux_signal` there is a new block that handles deopt NOPs. Zero does not have them, and so it currently encounters `ShouldNotReachHere()` when entering the block and doing either `os::Posix::ucontext_get_pc(uc)` or `NativeDeoptInstruction::is_deopt_at(pc)`.

This block should not be entered with Zero at all.