My recommendation for a solution is to teach pbuilder how to resolve cross dependencies and stop installing -cross packages outside a chroot. We tried it, it is/was painful - let's learn the lesson, not repeat previous mistakes.
How would this affect the continued availability of apt-cross and dpkg-cross? I'd hate to see them (or their functionality outside of pbuilder) go away completely, since I use them to manually build cross toolchains based on a modification of the method described here http://wiki.debian.org/EmdebianToolchain under the heading 'Build your own from sources'. I do this instead of using the pre-packaged toolchains or emchain, since I need to make the toolchains standalone for use outside of a Debian environment, using an alternate prefix so that they compile for use and install under /opt/.. instead of /usr/.. This is in support of a generic build environment for sofware that will run on my target Debian system, but which is not itself a Debian package. The generic build system, for reasons beyond my control, is not itself a Debian environment, and so the alternate prefix is necessary and useful.
I get great utility from the excellent Debian cross compiler packages, but my need to support them with alternate build prefix means that I need to make some manual changes to the rules makefiles of the binutils and gcc packages prior to compilation. These changes turn out in fact to be fairly trivial and generic, simply some replacement of hardcoded '/usr' paths with a prefix variable that is centrally defined. I'd be happy to post the diffs here and to submit them upstream in the appropriate manner if they could be of use to people beyond myself. If I were to do this, should I file a wishlist bug against binutils and gcc Debian packages with the patches?
Thanks, -Jim Heck