Fix infinite loop on empty variable name.

test/variables/empty/gyptest-empty.py

 #!/usr/bin/env python
-#
+
 # Copyright (c) 2015 Google Inc. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
 # found in the LICENSE file.
 
+"""
+Test that empty variable names don't cause infinite loops.
+"""
+
 import os
-import sys
 
-"""Cross-platform touch."""
+import TestGyp
 
-for fname in sys.argv[1:]:
-  if os.path.exists(fname):
-    os.utime(fname, None)
-  else:
-    open(fname, 'w').close()
+test = TestGyp.TestGyp()
+
+test.run_gyp('empty.gyp')
+
+test.pass_test()