Flip linux_chromium_clobber_rel_ng to GN.
Flip linux_chromium_clobber_rel_ng to GN.

This ensures that the CQ is doing one clobber build (on Linux),
better matches what the waterfall bots are doing, and removes
one more Linux GYP bot from the equation ...

R=ben@chromium.org
BUG=588018

Review URL: https://codereview.chromium.org/1709363002

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#376350}

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