As it happens, adding another architecture required almost no changes;
native 32-bit ppc build took only ARCH and a repo, qemu-ppc one still
has problems (/.host/entry hangs while unpacking setup for fakedata).

Proof of concept on a QS22:

  $ make ve/bare.tar.gz
  ** ARCH: ppc
  /bin/sh: rpmvercmp: command not found
  21:41:01 cleaning up
  21:41:03 initializing BUILDDIR: build/
  21:41:03 preparing distro config
  21:41:05 starting image build (coffee time)
  21:42:48 done (1:42)
  ** image: $TMP/out/bare-20120716-ppc.tar.gz [21M]