I have a need to build a OS X universal binary of an OCaml program. I  
found out how to do it (apologies if this is already posted, but I  
couldn't find a solution in the archives).

1. Install the PowerPC version of OCaml. Squirrel away /usr/local/bin/ 
ocamlopt and /usr/local/lib/ocaml (I just added ppc to their names).

2. Install the Intel version of OCaml.

3. To make a ppc version of the program, compile with /usr/local/bin/ 
ocamloptppc (no need to add any extra arguments), and link with /usr/ 
local/bin/ocamloptppc -ccopt "-arch ppc" -nostdlib -I /usr/local/lib/ 
ocamlppc.

That's it. When you've made both versions, merge them with lipo. ppc  
compilation and loading is a bit slow, but that's the only drawback  
I've found.

Sorry again if this is a bit obvious ...

Richard Bornat