Fix osmo-nitb build without libsmpp
diff --git a/openbsc/src/osmo-nitb/bsc_hack.c b/openbsc/src/osmo-nitb/bsc_hack.c
index 13fa1c5..172fb82 100644
--- a/openbsc/src/osmo-nitb/bsc_hack.c
+++ b/openbsc/src/osmo-nitb/bsc_hack.c
@@ -279,7 +279,9 @@
 		rc = bsc_bootstrap_network(int_mncc_recv, config_file);
 	if (rc < 0)
 		exit(1);
+#ifdef BUILD_SMPP
 	smpp_openbsc_set_net(bsc_gsmnet);
+#endif
 	bsc_api_init(bsc_gsmnet, msc_bsc_api());
 
 	bsc_gsmnet->ctrl = controlif_setup(bsc_gsmnet, 4249);