Parallelize test/mjsunit/es6/tail-call-megatest.js in order to avoid timeouts on slow architectures.

test/mjsunit/es6/tail-call-megatest-shard0.js

Index: test/mjsunit/es6/tail-call-megatest-shard0.js
diff --git a/test/mjsunit/es6/tail-call-megatest-shard0.js b/test/mjsunit/es6/tail-call-megatest-shard0.js
new file mode 100644
index 0000000000000000000000000000000000000000..fec69d33a55b4342da508fa52cb06d6afc94f8b5
--- /dev/null
+++ b/test/mjsunit/es6/tail-call-megatest-shard0.js
@@ -0,0 +1,15 @@
+// Copyright 2016 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// Flags: --allow-natives-syntax --harmony-tailcalls
+// TODO(v8:4698), TODO(ishell): support these cases.
+// Flags: --turbo --nostress-opt
+
+try {
+  load("mjsunit/es6/tail-call-megatest.js");
+} catch(e) {
+  load("test/mjsunit/es6/tail-call-megatest.js");
+}
+
+run_tests(0);