[Mingw-cross-env-list] ocaml cross compiler

[William]

Hello,

an ocaml cross-compiler is being put in mxe. This ocaml cross-compiler 
requires a tool to compile, which in turn requires ocaml in its native 
form. two options :
- (1) add ocaml to the mxe requirements, which means suggest to everyone 
who wants to set up mxe to install ocaml
- (2) add an ocaml-native.mk package, which will provide native ocaml.

As ocaml is not so much used I guess, the best solution would be (2), 
though it would add some significant compile time for the ones who want 
to compile and recompile everything on mxe.

Thoughts on this ?

Please go to https://github.com/mxe/mxe/pull/50#issuecomment-8720774

Regards,
William