We rooted out an obscure issue that was making the <cond test="arch"> not work. The checkins I made this morning may or may not conceptually the "the right way" to solve it, but it's the simplest fix I could think of (see postscript for note on what this issue was).
Now that the cond stuff works, we still need an answer on the ia32 architecture, where there are several different answers given when asking what the machine type is (i486, i686, others). Smells to me like those all ought to be equivalent from the point of view of the xml. How can we accomplish this?
