Make a joke out of it casually after they ask you to talk about yourself. Something like "By the way, just so you know, if I stutter, it's because I have a stutter. Not because I'm nervous. Well, not that nervous" They'll smile and say it's ok. If they don't, then it's probably not right for you anyway! Remember that you're worth so much more than how you speak in an interview. Focus on your experience and the reason why you're applying for the position. Prepare for those things and try not to worry about your speech. Try to enjoy the opportunity to get better. And if it doesn't go to plan, fuck it. At least it's good experience for the next interview! The fact you're even going to it makes everyone on here proud. Now go enjoy it.