pyoxidizer: default to a meaningless release instead of hardcoding 5.8 This way we don't advertise the wrong version, or if we do it's really obvious. To be honest, I'm not even sure that `VERSION` should be optional, but I also have never used the packaging tools so far, this is simply something I saw. Differential Revision: https://phab.mercurial-scm.org/D11360