Since NeXTStep v3.0, mid-90s, the compiler toolchain had the ability to compile multiple-architecture binaries. Of course Apple bought NeXT and much of OS X is

Since NeXTStep v3.0, mid-90s, the compiler toolchain had the ability to compile multiple-architecture binaries. Of course Apple bought NeXT and much of OS X is still based on it. I forget the exact magic method, and don't know if it is still in shipping versions of OS X, but I would be surprised if at least internal-to-Apple versions of their compiler and toolchain didn't still have this available for use.