Fix path handling in tools/version.dart so that it does not matter where we call this from.

tools/version.dart

Index: tools/version.dart
===================================================================
--- tools/version.dart	(revision 13524)
+++ tools/version.dart	(working copy)
@@ -1,3 +1,4 @@
+#!/usr/bin/env dart
 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // 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.
@@ -2,6 +3,8 @@
 
-#import("testing/dart/version.dart");
+import "dart:io";
+import "testing/dart/version.dart";
 
 void main() {
-  Version version = new Version("tools/VERSION");
+  Path scriptPath = new Path(new Options().script).directoryPath;
+  Version version = new Version(scriptPath.append("VERSION"));
   Future f = version.getVersion();