(1) Your build cannot possibly be fast enough. Your boss will almost always think it is a waste of time to spend time speeding up your build, but if you work out the math in terms of minutes spent and minutes saved, the payoff time can be as little as a week for spending 2 days improving your build.
(2) Your build cannot be fast enough. Quite likely you have a machine that was chosen to be crazy cheap (Dell) or crazy beautiful (Mac) but not chosen to be crazy fast. A crazy fast machine with an SSD and the best CPU you can get will improve your productivity enough to pay for itself in 2 months or so if you do the math. Your boss won't believe it, so you might just get one for yourself.
(3) It never hurts to get up and move around
(4) It is not a bad idea to stare at the screen and think. In fact, carefully reading the output of your build should piss you off enough that you do something at (1)
(5) Overall it is dangerous to juggle a large number of balls in the area, but one exception to this is to carve out a single task you can work on while waiting for builds and make
switching to and from that task as easy as possible. This task can be anything that makes progress towards your goals, such as sorting the backlog, reading technical documentation, etc.
(6) Set up some kind of chime to ring when your build is done, that will help you get back to it. It's one of those things that people don't seem to do, but it works.