Make upgrade, then make rescue

If you haven’t done it before, you can use ‘make rescue’ to build a tiny base system on DragonFly, for use when /usr goes missing, for when your disk is encrypted, and other rather catastrophic problems.  It should be in sync with the rest of the system, which is why ‘make rescue’ can be part of a buildworld process.  I’m mentioning this because currently, ‘make upgrade’ should be done first.