This fixes the static library build of this target on Linux.

BUG=angleproject:1270

Change-Id: Id65bd9b7136918829f385920b540a4df83650c6f
Reviewed-on: https://chromium-review.googlesource.com/320615Tested-by: Kenneth Russell <kbr@chromium.org>
Tryjob-Request: Kenneth Russell <kbr@chromium.org>
Reviewed-by: Corentin Wallez <cwallez@chromium.org>
Reviewed-by: Jamie Madill <jmadill@chromium.org>