check-config.sh: add SECCOMP_FILTER

The check of seccomp filter support was needed.

Ref: https://github.com/opencontainers/runc/pull/2867

Signed-off-by: Kenta Tada <Kenta.Tada@sony.com>

contrib/check-config.sh

@@ -226,6 +226,7 @@ echo 'Optional Features:'
 }
 {
 	check_flags SECCOMP
+	check_flags SECCOMP_FILTER
 }
 {
 	check_flags CGROUP_PIDS