buildroot

package/audit: add support for host variant

host-libsemanage requires host-audit to compile, therefore this patch
adds a host variant for the audit package.

Signed-off-by: Adam Duskett <Aduskett@gmail.com>
[Thomas: remove libcap-ng usage for now, rework commit log.]
Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>