Dude, just tell him, I've had crushes on a lot of my friends, and just telling them "hey bro, I find you really attractive, but I ain't want it to f**k up our friendship, so like do with that info whatever you want" seems to do the trick pretty consistently.
You might get stabbed in the feels a little bit tho. I once told this to a friend, she told me "ofc you do, everyone does", then I asked her more directly, and she said "I'm gonna assume you're joking".