Use quieter test output when running tests on Travis CI

[frewsxcv]

Currently on Travis CI for this repository, running the full test suite results in one having to download the raw log because the entire log is too long to fit in Travis CI's web UI. It also causes my browser tab to halt for a few seconds to render. I propose we turn on the quieter test output for test running on Travis CI. This will also make it easier to find test failures for PRs where there are failures.

[alexcrichton]

Sounds like a great idea!

[frewsxcv]

@alexcrichton Have any suggestions about how to accomplish this with rustbuild?

[alexcrichton]

Perhaps could be a ./configure option which is threaded through to the tests themselves?

[frewsxcv]

Nevermind, I guess this was intentionally turned off in 2727866

[alexcrichton]

Ah yeah this was explicitly re-enabled to help diagnose flaky failures we've been having.