show something when starting to build targets when verbose = 2

[kendonB]

Prework

• Read and abide by drake's code of conduct.
• Search for duplicates among the existing issues, both open and closed.

Proposal

Would be good to have something show before the first target is done to indicate that building has started when verbose = 2. Maybe even a fake progress bar with 1000 ticks and one tick done so that it shows 0%?

[wlandau]

Good call, now an empty progress bar should appear right before targets start.