Unless the bearer of that name specifies how he wants it pronounced, I would say "Allen - court", just as I say those two English words -- ignoring the i . I believe the French say something that is close to the English "ell-on-COOR" -- possibly "eye-on-COOR". Your best bet is always to ask the person, if available, how to pronounce it.
New words, one handy idiom, and a 2-minute quiz — delivered to your inbox to keep your streak alive.