Otherwise building on armel fails with

checking for linux SRCARCH... configure: error: architecture arm-unknown-linux-gnueabi not supported

See https://bugs.launchpad.net/ubuntu/+source/lxc/+bug/745884 for details.
Signed-off-by: Serge Hallyn <serge.hallyn@canonical.com>
Signed-off-by: Daniel Lezcano <dlezcano@fr.ibm.com>