mb: fix gn config for CFI Linux bot
mb: fix gn config for CFI Linux bot

This is a follow up to https://codereview.chromium.org/1478863004/

BUG=481692,561677

Review URL: https://codereview.chromium.org/1484413002

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#362550}

axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk,axinging/chromium-crosswalk