http://www.trevorpounds.com/blog/?p=111

apt-get install ia32-libs ia32-libs-gtk

gcc -m32 (see http://wiki.debian.org/DebianAMD64Faq)

linux32 make

Building an i386 kernel package on an amd64 machine without chroot

In addition to ia32-libs, install gcc-arm-linux-gnueabi (armel), or gcc-arm-linux-gnueabihf (armhf).

Using QEMU to create a rootfs, and build packages inside with the usual tools like pbuilder.

Using a chroot, and then qemu to be able to run the binaries.