Add timing report for build step

[faultyserver]

As the projects that I'm working on grow in size, compile times are growing upwards of 10 seconds, which makes me really glad to have sentry running to save as much time as possible with automatically building/running on save. However, I think it'd be nice to see just how long the build step took to complete as part of the output of sentry.

The main reason is that I want to do as much as I can to avoid increasing compile times from new additions, which is much easier when I can see exactly how long things are taking as I make changes in real time. I've currently got all of my build steps configured as: build: time -p shards build as a workaround, but that feels messy and adds more extra lines to the output.

Just a single line like "Build succeeded in 0.00 seconds" would be sufficient for me. Maybe this could be behind a --verbose flag/config for the sake of people who aren't interested in it?

[samueleaton]

oooh i like this idea. maybe even just piggyback this on the current --info flag.