Gay friend has a crush on me. Any advice?

I've known this guy since grade school, and I never really spoke with him that much, but today, he revealed that back in high school, he's had a huge crush on me, and is being very flirtatious and such............which is extremely awkward and embarrassing.

Don't get me wrong, I completely support LGBT rights and such, but I'm just not one of them myself.

He's a nice guy and all, but I just don't feel that way towards men, only towards women.

Anyone have any advice for me?