minijail: Add option to enter a new IPC namespace

Export this feature through the '-l' option to minijail0.

TEST=run minijail0 with the -l option, check that the executed program
is in a different ipc namesspace with /proc/self/ns/ipc.
BUG=b/25770648

Change-Id: Ia8f72cc59160fc736c8a58cb68d9894f9c92281c
Signed-off-by: Dylan Reid <dgreid@chromium.org>
diff --git a/libminijail.h b/libminijail.h
index e7f24ce..9d92462 100644
--- a/libminijail.h
+++ b/libminijail.h
@@ -50,6 +50,7 @@
 void minijail_use_caps(struct minijail *j, uint64_t capmask);
 void minijail_namespace_vfs(struct minijail *j);
 void minijail_namespace_enter_vfs(struct minijail *j, const char *ns_path);
+void minijail_namespace_ipc(struct minijail *j);
 void minijail_namespace_net(struct minijail *j);
 void minijail_namespace_enter_net(struct minijail *j, const char *ns_path);
 /* Implies namespace_vfs and remount_proc_readonly.