Yes, you have to wait until 2021 to include these costs (site preparation, driveway, drainage, pad, etc.) in the total cost of the building.
You cannot begin depreciating (deducting) the cost to construct the building until the year in which it is placed in service (i.e. completed and started being used for business purposes). For that reason, you do not enter the building as a building asset until 2021.
