README: replace sh test/test.sh with make cross
diff --git a/README b/README
index b7ad4e9..4d81081 100644
--- a/README
+++ b/README
@@ -152,7 +152,7 @@
 
 To run the cross-language test suite, please run:
 
-          sh test/test.sh
+          make cross
 
 This will run a set of tests that use different language clients and
 servers.