Symlink to rules_testing in soong integration test.

Bug: None
Test: CI
Change-Id: Ib2667798ba4ae330ff46978b37c9c50a5a0cd477
diff --git a/tests/lib.sh b/tests/lib.sh
index 0766d85..dbb10b7 100644
--- a/tests/lib.sh
+++ b/tests/lib.sh
@@ -158,6 +158,7 @@
   symlink_directory external/bazelbuild-rules_python
   symlink_directory external/bazelbuild-rules_java
   symlink_directory external/bazelbuild-rules_rust
+  symlink_directory external/bazelbuild-rules_testing
   symlink_directory external/rust/crates/tinyjson
 
   symlink_file WORKSPACE