I'd expect both the earlier 1.2TSI engines were chain driven, but by 2015 cars, the new engines should be fitted, I'm certainly walk away from a newly reg'd
Ibiza from late 2014 on if it had either of the older engines in it.
If in doubt I'd be checking the engine code, or if viewing the car, check to make sure that the turbo is at the rear of the engine and the inlet on the front of the engine, another hint that it has a belt drive is if it has a black plastic cover on the RHS of the engine.