Should I be able to build cross gcc 4.x on Cygwin?

[Rick Mann <rmann@xxxxxxxxxxxxxxx>]

I've been able to build an xscale-elf-targeted GCC (and binutils and  
newlib) on Mac OS X. Now I have to do the same thing on Cygwin (ugh),  
and it doesn't work.

One thing is that Cygwin has GCC 3.4, not 4.x.

Looking around, the GCC installation notes seem to imply that 3.4 can  
build 4.x, so I'm wondering if there's something in particular I need  
to watch out for?

TIA,
Rick