core: create inaccessible nodes for users when making runtime dirs

To support ProtectHome=y in a user namespace (which mounts the inaccessible
nodes), the nodes need to be accessible by the user. Create these paths and
devices in the user runtime directory so they can be used later if needed.

src/test/test-dev-setup.c

@@ -20,7 +20,8 @@ int main(int argc, char *argv[]) {
         f = prefix_roota(p, "/run");
         assert_se(mkdir(f, 0755) >= 0);
 
-        assert_se(make_inaccessible_nodes(p, 1, 1) >= 0);
+        f = prefix_roota(p, "/run/systemd");
+        assert_se(make_inaccessible_nodes(f, 1, 1) >= 0);
 
         f = prefix_roota(p, "/run/systemd/inaccessible/reg");
         assert_se(stat(f, &st) >= 0);