libweave: Build weave example for ubuntu

BUG=brillo:1275
TEST=libweave/examples/ubuntu/build.sh

Change-Id: I6b0d97cc27077c8d64d095419cce34da3d79b0cd
Reviewed-on: https://chromium-review.googlesource.com/297005
Commit-Queue: Vitaly Buka <vitalybuka@chromium.org>
Trybot-Ready: Vitaly Buka <vitalybuka@chromium.org>
Tested-by: Vitaly Buka <vitalybuka@chromium.org>
Reviewed-by: Alex Vakulenko <avakulenko@chromium.org>