i think this is already stalemate because blacks king cant move anywhere because of the G and H file pawn structure. also no matter what pawn you take out with your bishop the others will be locked up and his king cant movee, creating stalemate
But by capturing the f-pawn en-passant, black then has two possible legal moves as BDP has already explained. So therefore not stalemate, avoiding this is something which needed to be considered.