Support cross-compiling for iOS (armv7)

While it may be a working implementation now, though, it's basically dead code and will likely bitrot/fall out of date quickly.

I suppose we could leave this in for now as it's not affecting too many others. I would be more inclined to make them no-ops, however, (possibly commented out). I'm worried that if apple rejected the split-stack patch that we're modifying registers which aren't supposed to be modified (even when we don't need to)