Mock can't build x86_64 packages

[Jonathan Ryshpan]

On Fri, 2009-10-02 at 11:00 -0400, Todd Zullinger wrote:
> Clodoaldo Neto wrote:
> > Trying to build rpm packages with mock in F11 i386:
> >
> > I can build i386 packages but not x86_64 as I get this:
> 
> You can't build for x86_64 on i386.  Doing it the other way around
> works fine though.

Why not?  I thought that cross compilation worked on any two processors
(within reason).

jon