util-linux: add host variant for host-lttng-babeltrace

lttng-babeltrace needs libuuid, which is provided by util-linux, and
since we want to build lttng-babeltrace for the host, we need to build
libuuid for the host. It's a shame that libuuid is part of such a big
package as util-linux.

Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>