openbmc: enable libseccomp for systemd

This change required as a part of privilege separation work:
  https://github.com/openbmc/openbmc/issues/3383

Seccomp support enables sandboxing in systemd:
  https://www.freedesktop.org/software/systemd/man/systemd.exec.html#Sandboxing

Signed-off-by: Anton D. Kachalov <gmouse@google.com>
Change-Id: If7ff257103c4aa40dae5f64256bf60d8a30fbf59
diff --git a/meta-phosphor/recipes-core/systemd/systemd_%.bbappend b/meta-phosphor/recipes-core/systemd/systemd_%.bbappend
index 8a07277..9d4dfc7 100644
--- a/meta-phosphor/recipes-core/systemd/systemd_%.bbappend
+++ b/meta-phosphor/recipes-core/systemd/systemd_%.bbappend
@@ -10,6 +10,7 @@
         pam \
         randomseed \
         resolved \
+        seccomp \
         sysusers \
         sysvinit \
         timedated \