He’s a muslim. Born a muslim/always a muslim. Unless he converted, which there is no evidence of having been done. In which case, he would be an infidel ripe for beheading.
While I could agree that he is or was technically a muslim, and given that he now claims to not be a muslim he is an apostate (which brings up the question of why people would think an apostate would be well received by the islamic world when they are sworn to kill him) I think he views religion as something to be manipulated for personal advantage. Obviously he's not really a Christian, but he did his best to play up his claims during the election.