The sysroot only contains headers for gcc6, not gcc4.8 which is the version installed on the coverage bots.

Bug: chromium:837238
Change-Id: Ifd9b53dae510b969b4ef5ec8c1c2684eb92a94fa
Reviewed-on: https://chromium-review.googlesource.com/1059150Reviewed-by: Michael Achenbach <machenbach@chromium.org>
Commit-Queue: Tobias Tebbi <tebbi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#53186}