Would you rather I just made the os-version/${MACHINE_ARCH} format the
default?  Or use the os-version/${MACHINE_ARCH} format if OBJMACHINE
is set?

Right now, things are horribly broken if you have multiple arch's
sharing a pkgsrc tree and try to build binary packages from more than
one.  You may not do this, but the fact that we support putting
MACHINE_ARCH in the work directory name means that we're at least
pretending to support this configuration.

I want to fix this in a way which doesn't require me to do anything
complicated in mk.conf, and especially not something which requires me
to whack the files on each builder in different ways.  Please propose
an alternate solution if you don't like any of what I've suggested.

					- Bill