packaging: rework version detection and declaration (issue4912) Previously the -rc in our rc tags got dropped, meaning that those packages looked newer to the packaging system than the later release build. This rectifies the issue, though some damage may already have been done on 3.6-rc builds. I'm mostly cargo-culting the RPM version format - there don't appear to be rules for RPM about how to handle this. Hopefully an RPM enthusiast can fix up what I've done as a followup.