Consider making that build report on its progress. Not outputting anything is awful UX because you can’t tell if anything’s happening or it’s stuck (which is bad because if it’s stuck, you are wasting your time waiting for it; and you also have no idea where exactly it’s stuck to be able to fix that). Travis’ auto termination is there specifically to kill stuck commands – for our mutual benefit, as per above.
There is no supported way. travis_wait saves output to a log file and prints it all at the end. You may try tail -F "travis_wait_${$}.log" & (make sure to save the job’s PID to kill it at the end) but this is not a supported way (thus may break in the future) and will get you a duplicate of the output at the end.
You may consider start_spinner/stop_spinner from https://github.com/matthew-brett/multibuild/blob/master/common_utils.sh as an alternative.