As long as your kernel AND cpu support it, you can cross compile for
it. Maybe you can create a shell script that will pass your build
scripts into a 64bit chroot, then to a 32bit chroot? That would be
faster than a VM, won't require you to do it twice in a row, and will
eliminate the time it takes you to realize that the first build is
done and start the other. You can also have it play a sound based on
if it failed or succeeded, and put different sounds for each arch.

-- 
Kris
"Piki"
Ark Linux Webmaster
Trinity Desktop Environment Packager