Board Head offers GF bread on the sandwiches. Questionable prep area use you best judgement. I have a layover that was supposed to be on the plane and got pulled off and wanted for 6 hours so I took a risk. No problems
They knew what I could have. No rice (pasta is in it) or pita, but the shawarma salad was tasty and gluten free.
Boars Head terminal A - offers GF bread for make your own sandwiches. Also lots of GF bars, treats, and even pre-packaged cookies at the snack stands around Boars Head (including fruit, chips, etc).