Add the seccomp build tag for s390x now runc updated

This was waiting for runc bump see https://github.com/docker/docker/issues/23171
runc was bumped in https://github.com/docker/docker/pull/23603

Fixes #23171

Signed-off-by: Justin Cormack <justin.cormack@docker.com>

Dockerfile.s390x

@@ -161,7 +161,7 @@ RUN useradd --create-home --gid docker unprivilegeduser
 
 VOLUME /var/lib/docker
 WORKDIR /go/src/github.com/docker/docker
-ENV DOCKER_BUILDTAGS apparmor selinux
+ENV DOCKER_BUILDTAGS apparmor selinux seccomp
 
 # Let us use a .bashrc file
 RUN ln -sfv $PWD/.bashrc ~/.bashrc