It is a common thing with alloy wheels and Brembro rotors, and for a while Cadillac was replacing wheels because of it, until they figured out the solution at each tire rotation
it's an easy fix: remove the wheel, use a scotch-brite pad and clean the back side of the wheel where it touches the rotor, simple everyday brake cleaner works well. I don't whats going on between the two that causes the noise, the wheel isn't loose and there is no danger of it coming loose, they for some reason like to make a clicking noise (almost like a bad CV joint). It goes a way with a simple cleaning.