Allow Linux packages to be built with a non-jessie sysroot

BUG=751812
R=thestig@chromium.org
TBR=rkc@chromium.org

Change-Id: I3d8ff471df1377c9c4cf184044abd14700b8b8cf
Reviewed-on: https://chromium-review.googlesource.com/599029
Reviewed-by: Thomas Anderson <thomasanderson@chromium.org>
Reviewed-by: Lei Zhang <thestig@chromium.org>
Commit-Queue: Thomas Anderson <thomasanderson@chromium.org>
Cr-Commit-Position: refs/heads/master@{#491581}
6 files changed