Build fixes

Some fixes for build environments where dependencies are installed in
distinct directories.

Change-Id: I38808fd2911747b266ee6fde91187a88dd7ae355
diff --git a/openbsc/tests/sgsn/Makefile.am b/openbsc/tests/sgsn/Makefile.am
index 6371707..d148c48 100644
--- a/openbsc/tests/sgsn/Makefile.am
+++ b/openbsc/tests/sgsn/Makefile.am
@@ -7,6 +7,7 @@
 	-Wall \
 	-ggdb3 \
 	$(LIBOSMOCORE_CFLAGS) \
+	$(LIBOSMOABIS_CFLAGS) \
 	$(LIBOSMOGSM_CFLAGS) \
 	$(LIBCARES_CFLAGS) \
 	$(NULL)
@@ -63,7 +64,7 @@
 	$(LIBOSMOGB_LIBS) \
 	$(LIBCARES_LIBS) \
 	$(LIBCRYPTO_LIBS) \
-	-lgtp \
+	$(LIBGTP_LIBS) \
 	-lrt \
 	$(NULL)
 if BUILD_IU