Comment 5 for bug 1319153

By the way, for the case of an amd64 chroot on an i386 host system, we'll deal with this by just creating a native amd64 chroot; this is our only option because there's no i386-to-amd64 cross-compiler as such in the archive (and "gcc -m64" is a somewhat different kettle of fish that requires explicit build system support). This is perfectly workable, but only if you've taken special measures to install a 64-bit kernel on the i386 system so that it can execute 64-bit binaries.

I suspect that this is a fairly niche case; i386 chroot on amd64 host will likely be rather more common.