I've always thought the method of modifying your local mirrorlist, running mkarchroot, then reverting the changes to be more tedious than necessary for creation of i686 chroots on x86_64. My recent work with setting up a dedicated build server gave me plenty of time and an excuse to actually do something about it. As such, I've put together a little patch that allows specification of creation of an i686 chroot at runtime. When set, this flag will automatically modify your local mirrorlist, create the requested i686 chroot, then revert the changes to the mirrorlist file. I don't know if others would find this useful or not, but I figured it wouldn't hurt to post it.
mkarchroot-setarch.diff
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