Travis builds hang at the end

[native-api]

Job still running after "Done. Your build exited with 0."

Accordng to Windows build hangs after Done exit 0, this happens if some background processes are still running. To compare process lists before and after, e.g. run ps -W | sort at appropriate moments, then diff the outputs. To get the command line of the culprit, read /proc/<pid>/cmdline as per https://superuser.com/questions/1247844/full-command-text-with-ps-on-cygwin.