Add a {linux,mac}-dawn-rel builders to be triggered from the Dawn CQ

These builder will run the dawn_end2end_tests on the GPU swarming
bots through the Chromium recipe.

BUG=chromium:901830

Change-Id: I2e462a872ff708d751cee9fd9c21c69761736690
Reviewed-on: https://chromium-review.googlesource.com/c/1341547
Commit-Queue: Andrii Shyshkalov <tandrii@chromium.org>
Reviewed-by: Andrii Shyshkalov <tandrii@chromium.org>
Cr-Commit-Position: refs/heads/master@{#609756}
2 files changed