I think people do not often cross compile Lisp code for other platforms.
Therefore not so many information is published. You can search the mailing list.
But also, as I said, you should understand how the build process works.
Some weeks ago I introduced one more abstraction in the compiler: machine objects. They group information about a target platform, such as types, integer sizes, compilers, libraries, etc. The idea would be that a single compiler should be capable of producing code for multiple targets, automating what people are already doing.
However, the fact that lisp code needs to load former instances of itself to compile new code may still have subtle side effects -- i.e. one macro inspects the value of most-positive-fixnum and uses that value as is instead of the symbol name to produce types, optimized code, etc. This means that cross-compiling in the lisp world is not that easy and for certain type of code it might be even impossible.