ninja windows: make sure there's a trailing slash on $(VCInstallDir)

test/win/vs-macros/test_exists.py

Index: test/win/vs-macros/test_exists.py
diff --git a/test/win/vs-macros/test_exists.py b/test/win/vs-macros/test_exists.py
new file mode 100644
index 0000000000000000000000000000000000000000..f5c90ad6f271ee64762e706fbe6347038fda1c25
--- /dev/null
+++ b/test/win/vs-macros/test_exists.py
@@ -0,0 +1,10 @@
+# Copyright (c) 2012 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.
+
+import os
+import sys
+
+if not os.path.exists(sys.argv[1]):
+  raise
+open(sys.argv[2], 'w').close()