update hooks: slip in public butterfly overlay

For people who have stout builds already, regen their board configs
so that they also include the public overlay.

BUG=chrome-os-partner:23327
TEST='BUG=chrome-os-partner:22327
TEST=`./update_chroot` converts a private-only /build/butterfly to include
the public repo

CQ-DEPEND=Ib12f784316e7ddfef608f2893f506915fbc10f1f

Change-Id: I349724e57d1c82bd1785d03f4ebb3d7a8160a3ab
Reviewed-on: https://chromium-review.googlesource.com/175545
Reviewed-by: Mike Frysinger <vapier@chromium.org>
Tested-by: Shawn Nematbakhsh <shawnn@chromium.org>
Commit-Queue: Mike Frysinger <vapier@chromium.org>
1 file changed