Watch command does not exit when interrupt signal is sent

[mky2]

After executing the command tectonic -X watch, when I press Ctrl + C sending the interrupt signal, it seems like watchexec has received the signal successfully, but the program does not terminate. Upon testing, it seems that adding action.quit_gracefully or action.quit in https://github.com/tectonic-typesetting/tectonic/blob/82484dbbfd698944c9d29cf6c0944c17e95d1e53/src/bin/tectonic/v2cli/commands/watch.rs#L138-L143 will do the job. But I'm not sure if it is considered a "hack", or perhaps it is an intended behaviour that the interrupt signal only stop the underlying jobs and not the actual tectonic program.