mb_config.pyl: add linux-dawn-rel and mac-dawn-rel

BUG=chromium:901830

Change-Id: I8cea07cc08ca559014cf68d75f4eef65a838efb0
Reviewed-on: https://chromium-review.googlesource.com/c/1341844
Reviewed-by: Stephen Martinis <martiniss@chromium.org>
Commit-Queue: Corentin Wallez <cwallez@chromium.org>
Cr-Commit-Position: refs/heads/master@{#609635}
1 file changed