Make build with capabilities optional
Fixes: https://pagure.io/gssproxy/issue/239
Signed-off-by: Stanislav Levin <slev@altlinux.org>
[rharwood@redhat.com: rebase, commit message]
Reviewed-by: Robbie Harwood <rharwood@redhat.com>
Reviewed-by: Simo Sorce <simo@redhat.com>