Hi All,
As part of the 11.07 cycle I've completed an initial implementation to live-build3 for cross build support. This means you can be on an intel box and assemble your own arm rootfs images. Generally speaking this results in a faster build than running on native arm hardware.
This code should be considered alpha quality. There are bugs. There are hacks which will disappear as the implementation improves.
A HOWTO can be found here:
https://wiki.linaro.org/LiveHelper/Cross
If you run into issues please either file a bug in launchpad https://bugs.launchpad.net/linaro-ubuntu , post to the list, or grab me on irc.