remove duplication between check and pages, and make a build job
The check
job is really a build job here, since it actually does
build the website. It just doesn't keep artifacts around... So let's
do that, and make the pages
job just reuse those instead of
rebuilding from scratch.
This is part of migrating torspec to a static component, as we need artifacts for the built site to be sent in to the static component system.