If the remote stub sends a specific error message instead of just a E??
code, we can use this to display a more informative error message
instead of just the generic "unable to attach" message.
I write a test for this using the SB API.
On the console this will show up like:
(lldb) process attach ...
error: attach failed: <STUB-MESSAGE>
if the stub supports error messages, or:
error: attach failed: "Error ??"
if it doesn't.