libosmo-mgcp-client: add -no-undefined to *_la_LDFLAGS

Make sure that there is no undefined references in shared libraries.

Change-Id: If6aa8016026beb8bad735987f3ab6e0d114b86a5
diff --git a/src/libosmo-mgcp-client/Makefile.am b/src/libosmo-mgcp-client/Makefile.am
index 2c5c653..fffb42a 100644
--- a/src/libosmo-mgcp-client/Makefile.am
+++ b/src/libosmo-mgcp-client/Makefile.am
@@ -35,4 +35,8 @@
 	mgcp_client_pool.c \
 	$(NULL)
 
-libosmo_mgcp_client_la_LDFLAGS = $(AM_LDFLAGS) -version-info $(MGCP_CLIENT_LIBVERSION)
+libosmo_mgcp_client_la_LDFLAGS = \
+	$(AM_LDFLAGS) \
+	-version-info $(MGCP_CLIENT_LIBVERSION) \
+	-no-undefined \
+	$(NULL)