V1 is calculated for weight and other factors, but runway length isn't one of them. As one of these guys said "if you were taking off from Bonneville Salt Flats the calculated V1 would be the same as from any airfield.
Whilst they are correct in one way, what will be the case on some airfields is that the runway length would restrict the TAKE OFF MASS, this take off mass would then dictate the V1, so you might have the same V1 at Bonneville as a shorter runway, but only up to a more limited Max TO on the shorter runway. Also, on a longer runway you can have a range of V1 whereas if the TO mass is restricted by runway length there will only be the one V1.