server: Fix dependency on libosmo-rspro.la

Change-Id: Ia05a5f0f01999b32fd10d76694e95df9b1ccb207
diff --git a/src/server/Makefile.am b/src/server/Makefile.am
index ce7843b..fe937b6 100644
--- a/src/server/Makefile.am
+++ b/src/server/Makefile.am
@@ -11,4 +11,4 @@
 remsim_server_SOURCES = remsim_server.c rspro_server.c rest_api.c ../rspro_util.c ../slotmap.c ../debug.c
 remsim_server_LDADD = $(OSMOCORE_LIBS) $(OSMOGSM_LIBS) $(OSMOABIS_LIBS) \
 		      $(ULFIUS_LIBS) $(JANSSON_LIBS) \
-		      ../libosmo-rspro.la
+		      $(top_builddir)/src/libosmo-rspro.la