Add test directive to include other files used by a test in its compiled output directory.

tests/standalone/io/regress_21160_test.dart

Index: tests/standalone/io/regress_21160_test.dart
diff --git a/tests/standalone/io/regress_21160_test.dart b/tests/standalone/io/regress_21160_test.dart
index b3d39f17251b8e4975bc36f7e8a40d0a4939657a..c4c4f13e36c3abf5af89cb8e857d01000dc1ec9b 100644
--- a/tests/standalone/io/regress_21160_test.dart
+++ b/tests/standalone/io/regress_21160_test.dart
@@ -2,6 +2,10 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
+// OtherResources=certificates/server_chain.pem
+// OtherResources=certificates/server_key.pem
+// OtherResources=certificates/trusted_certs.pem
+
 import "package:expect/expect.dart";
 import "package:path/path.dart";
 import "package:async_helper/async_helper.dart";