Make Platform.executable return a fully qualified path the the executable

sdk/lib/io/platform.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.
 
 part of dart.io;
 
 /**
  * Information about the environment in which the current program is running.
  *
  * Platform provides information such as the operating system,
@@ skipping 21 matching lines @@
  * variables in a [Map] that contains key-value pairs of strings. The Map is
  * unmodifiable. This sample shows how to get the value of the `PATH`
  * environment variable.
  *
  *     import 'dart:io' show Platform;
  *
  *     void main() {
  *       Map<String, String> envVars = Platform.environment;
  *       print(envVars['PATH']);
  *     }
- * 
+ *
  * ## Determine the OS
  *
  * You can get the name of the operating system as a string with the
  * [operatingSystem] getter. You can also use one of the static boolean
  * getters: [isMacOS], [isLinux], and [isWindows].
  *
  *     import 'dart:io' show Platform, stdout;
  *
  *     void main() {
  *       // Get the operating system as a string.
  *       String os = Platform.operatingSystem;
  *       // Or, use a predicate getter.
  *       if (Platform.isMacOS) {
- *         Print('is a Mac'); 
+ *         Print('is a Mac');
  *       } else {
  *        print('is not a Mac');
  *       }
  *     }
  *
  * ## Other resources
  *
  * [Dart by Example](https://www.dartlang.org/dart-by-example/#dart-io-and-command-line-apps)
- * provides additional task-oriented code samples that show how to use 
+ * provides additional task-oriented code samples that show how to use
  * various API from the [dart:io] library.
  */
 class Platform {
   static final _numberOfProcessors = _Platform.numberOfProcessors;
   static final _pathSeparator = _Platform.pathSeparator;
   static final _operatingSystem = _Platform.operatingSystem;
   static final _localHostname = _Platform.localHostname;
   static final _version = _Platform.version;
 
   /**
@@ skipping 48 matching lines @@
    * returned on Windows is therefore case-insensitive and will convert
    * all keys to upper case. On other platforms the returned map is
    * a standard case-sensitive map.
    */
   static Map<String, String> get environment => _Platform.environment;
 
   /**
    * Returns the path of the executable used to run the script in this
    * isolate.
    *
+   * If supported by the platform the returned path will be absolute.
+   *
    * If the execution environment does not support [executable] an empty
    * string is returned.
    */
   static String get executable => _Platform.executable;
 
   /**
    * Returns the absolute URI of the script being run in this
    * isolate.
    *
    * If the script argument on the command line is relative,
@@ skipping 30 matching lines @@
   /**
    * Returns the version of the current Dart runtime.
    *
    * The returned `String` is formatted as the
    * [semver](http://semver.org) version string of the current dart
    * runtime, possibly followed by whitespace and other version and
    * build details.
    */
   static String get version => _version;
 }