both native and cross in the same build directory

[David Byron]

I'm curious if there's more support for building both native and cross tools in
the same build directory than there was when these messages was written:

http://sourceware.org/ml/automake/2002-06/msg00149.html
http://sourceware.org/ml/automake/2002-07/msg00060.html

I didn't see anything in the autoconf change log.

I may just be curious to dive in and try to add it if that's the next step.  I
could use a few pointers though as I haven't modified either tool so far.

Thanks much.

-DB