I would assume the log is created at the end of the build, if it hangs it hangs. I have a similar problem in server mode. Even with verbose on, nothing gets printed.
That makes me think your problem will be hard to debug, but if you share a repo, you might at least help you identify the problem and potentially make sure Hugo write something about it in the next version rather than just hang.
The only thing I can think of, based on the information available, is that it’s the file locking that was introduced in 0.89, which would suggest that there’s another copy of hugo running from the same directory, possibly backgrounded.
If it happens again, and ps -ef | grep hugo doesn’t show another copy running, please run sw_vers and sysctl -n machdep.cpu.brand_string and report the results. Given the state of Apple’s QA, it wouldn’t surprise me if they’d managed to break file locking in some combination of OS release and architecture.