Make clang update script print nothing in the happy case where it needs to do nothing.

This is part of a few changes to make `gclient runhooks` less noisy.

Bug: 772741
Change-Id: If3d8621fc282a49488beac131a3519d2c141c482
Reviewed-on: https://chromium-review.googlesource.com/706826
Reviewed-by: Hans Wennborg <hans@chromium.org>
Commit-Queue: Nico Weber <thakis@chromium.org>
Cr-Original-Commit-Position: refs/heads/master@{#507413}
Cr-Mirrored-From: https://chromium.googlesource.com/chromium/src
Cr-Mirrored-Commit: f98681b809b1f9026b90fccfba6f1835c258146d
1 file changed