Use 9p over virtio to share files on the host with the guest domains. The files are accessible in the guests /hostfs directory.
This allows to use minimal copy-on-write clones of the base image as guest images, which in turn saves a lot of disk space.
Guest and network configuration is setup using the libvirt virtualization API. The [start|stop]_testing scripts have been updated accordingly. qemu/KVM does not currently support a hostfs, so the shared build tree mount has been dropped for now.
Reto Buerki