tests/.../Makefile.am avoid redundant linkage with librt

The librt is required for old glibc < 2.17 to get clock_gettime().
Since we do check the availability of this function libosmocore
and conditionally link it against librt, there is no need to do
such unconditional and redundant linkage here.

Change-Id: If587d16d2db677b97e3a0641027eb735af9c9c30
diff --git a/tests/msc_vlr/Makefile.am b/tests/msc_vlr/Makefile.am
index 29c5fb1..f9a9224 100644
--- a/tests/msc_vlr/Makefile.am
+++ b/tests/msc_vlr/Makefile.am
@@ -42,7 +42,6 @@
 	$(LIBOSMOGSUPCLIENT_LIBS) \
 	$(LIBRARY_GSM) \
 	-ldbi \
-	-lrt \
 	$(NULL)
 
 noinst_HEADERS = \
diff --git a/tests/sms_queue/Makefile.am b/tests/sms_queue/Makefile.am
index 81e017b..80189c7 100644
--- a/tests/sms_queue/Makefile.am
+++ b/tests/sms_queue/Makefile.am
@@ -45,7 +45,6 @@
 	$(LIBOSMOGSUPCLIENT_LIBS) \
 	$(LIBRARY_GSM) \
 	-ldbi \
-	-lrt \
 	$(NULL)
 
 sms_queue_test_LDFLAGS = \