[MLton] Win64 patches again

[Matthew Fluet]

On Mon, 4 Feb 2008, Wesley W. Terpstra wrote:
> cross-compiler-option-changed.patch:
>
> I earlier had people add the '-b' flag as gcc needed it for cross compiling. 
> Newer gcc no longer accepts this option. Instead, the platform prefixs the 
> gcc executable. This patch corrects this. If the old behaviour is needed for 
> old gcc, a simple shell wrapper works.
>
> Also, when cross compiling, not only gcc, but also ar and ranlib need the 
> executable prefix. The runtime/Makefile also presumed CC=gcc at one point.

Committed with minor changes:
   http://mlton.org/cgi-bin/viewsvn.cgi?rev=6403&view=rev