For what, fat binaries? That's pretty much what Mach-O format had from inception under NeXTSTEP, and survived until now. As it was said in the sibling comment,

For what, fat binaries? That's pretty much what Mach-O format had from inception under NeXTSTEP, and survived until now. As it was said in the sibling comment, iOS 9 is introducing a way to cut exactly the slice you need for a particular device.