What if . . .

Black simply leaves his clock to run out ? Is this game a draw in that case ?

It's a draw, because Black would have lost on time, but White can't win with material so it's a draw.  It's always a draw if the one who wins on time doesn't have enough material to mate.

But it's clear that white can win by checkmate if black moves his pawn.

I might have positioned the board wrong, though.

I think you mean this. On chess.com the game would be declared a draw but in a fide tournament the arbiter would declare the game won for white (even in a slightly more complicated position if white can show that mate is possible).

With the King on C8 and the Knight on C7, it would be checkmate... But it would take at least 5 moves without black moving the a pawn... Still.. there is sufficient material in that position. But I think you're right and that C.c would call it a draw anyway.

I think that chess.com should change the rules of this! Lets say this was an amazing combination leading to that position and black lets his time run out. Super silly!