Using build.sh for cross builds

[Bob Lee <glee%force10networks.com@localhost>]

        I'm trying to cross build on a Linux system.  I need to build powerpc, 
i386, and x86_64 targets.  From this we need to build the cross tools once, in 
a common location, and not rebuild each time we invoke build.sh.  I've tried 
'-u' option, but build.sh attempts to re-create cross tools every time.
        I can roll my own, but I'd like to try to use build.sh at least 
initially.

Thanks,
- bob