A number of times I've already started a regular upgrade of a building, then realised I can't afford to wait so many hours/days for it to finish - but it seems there's nothing you can do it about? Unlike, say, sending out a Geologist or Explorer where you can use gems to "halve" the remaining time (which I've only ever used once, needed to find more coal in less than 4 hours!). Perhaps a similar feature would make sense for building upgrades (or maybe I've just completely missed how to do it...).