When we detect a process that the native debugserver cannot handle, handoff the connection fd to the translated debugserver.
With this patch, debugging a translated app will only work when we invoke debugserver with --fd for its communication back to lldb. e.g. running 'debugserver localhost:2000 --attach=translated-app' will pass -fd=-1 as a command line argument to /Library/Apple/usr/libexec/oah/debugserver. Doing this properly would involve passing the same hostspec:portnum that debugserver received in this case -- but could we at least error out in DNBProcessAttach if communcation_fd==-1 so it's clear that this is not yet a supported workflow?