How to deal with inappropriate comments during interviews for academic positions?
Although the comment was absolutely inappropriate, it wasn't directed toward your friend and had nothing to do with the selection process.

The department chair took notice of the comment in your friend's presence.  We could hope the department chair will have taken appropriate action.

I think that's sufficient, especially since your friend is a candidate for a position.  If your friend believes he or she must do something further, your friend could write to the department chair, saying something like, "I couldn't help but hear Professor X's comment.  Have any students complained about his comments or demeanor?  Should I report his remark, and to whom?"  That puts the department chair on notice that you took notice, didn't like it, and are prepared to go further.