I brought it up explicitly. They need to know and it makes you more attractive to them, and they will take it into consideration when deciding who to offer the position through first. I emailed the search chair something like:
I greatly appreciate the opportunity to interview at XXX. I was wondering if you would be willing to give me a general sense of the job search timeline at XXX university? I completely understand if you are not able to share this information.The reason I ask is that I currently have an offer for a faculty position. In many ways, however, a position at YYY university position is a much better fit for what I am looking before as a faculty member because of W,A,Z.
You could email it after the search if it doesn't come up in the interview (some people might explicitly ask you if you have other offers)