Resolve the executable path on Mac OS when sym-linked

tests/standalone/io/platform_executable_test.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.
 //
 // Process test program to test process communication.
 
 library PlatformExecutableTest;
 
 import "dart:io";
 
@@ skipping 26 matching lines @@
   var result = processResult.stdout.trim();
   expectEquals(Platform.executable, result);
 }
 
 void testDartExecShouldNotBeInCurrentDir() {
   var type = FileSystemEntity.typeSync(platformExeName);
   expectEquals(FileSystemEntityType.NOT_FOUND, type);
 }
 
 void testShouldSucceedWithEmptyPathEnvironment() {
-  var command = Platform.isWindows ? 'dir' : 'ls';
+  var command = Platform.isWindows ? 'cmd' : 'ls';
   Process.runSync(command, [],
                   includeParentEnvironment: false,
                   environment: {_SCRIPT_KEY: 'yes', 'PATH': ''});
 }
 
 void testShouldSucceedWithSourcePlatformExecutable() {
-  //print('*** Running normally');
   verify(Platform.executable);
 }
 
 void testExeSymLinked(Directory dir) {
   var dirUri = new Uri.directory(dir.path);
   var link = new Link.fromUri(dirUri.resolve('dart_exe_link'));
   link.createSync(Platform.executable);
-  //print('*** Creating a sym-link to the executable');
   verify(link.path);
 }
 
 void testPathToDirWithExeSymLinked(Directory dir) {
   var dirUri = new Uri.directory(dir.path);
   var link = new Link.fromUri(dirUri.resolve('dart_exe_link'));
   link.createSync(Platform.executable);
-  //print('*** Path to a directory that contains a sym-link to dart bin');
   verify('dart_exe_link', altPath: dir.path);
 }
 
 /// Create a sym-link to the SDK directory and run 'dart' from that path
 void testExeDirSymLinked(Directory dir) {
   var dirUri = new Uri.directory(dir.path);
 
   var linkDirUri = dirUri.resolve('dart_bin_dir_link');
   var link = new Link.fromUri(linkDirUri);
 
   var exeFile = new File(Platform.executable);
 
   link.createSync(exeFile.parent.path);
 
   var linkedBin =
       new Uri.directory(linkDirUri.toFilePath()).resolve(platformExeName);
 
-  //print('*** Running in a sym-linked directory');
   verify(linkedBin.toFilePath());
 }
 
 void testPathPointsToSymLinkedSDKPath(Directory dir) {
   var dirUri = new Uri.directory(dir.path);
 
   var linkDirUri = dirUri.resolve('dart_bin_dir_link');
   var link = new Link.fromUri(linkDirUri);
 
   var exeFile = new File(Platform.executable);
 
   link.createSync(exeFile.parent.path);
 
-  //print('*** Path points to a sym-linked SDK dir');
   verify(platformExeName, altPath: link.path);
 }
 
 void testPathToSDKDir() {
   var exeFile = new File(Platform.executable);
   var binDirPath = exeFile.parent.path;
 
-  //print('*** Running with PATH env set to environment - fixed in 16994 - thanks!');
   verify(platformExeName, altPath: binDirPath);
 }
 
 void withTempDir(void test(Directory dir)) {
   var tempDir = Directory.systemTemp.createTempSync('dart.sdk.test.');
   try {
     test(tempDir);
   } finally {
     tempDir.deleteSync(recursive: true);
   }
 }
 
 String get platformExeName {
   var raw = new Uri.file(Platform.executable);
   return raw.pathSegments.last;
 }
 
 String get scriptPath => Platform.script.toFilePath();
 
 void main() {
   if (Platform.environment.containsKey(_SCRIPT_KEY)) {
     print(Platform.executable);
     return;
   }
 
   testDartExecShouldNotBeInCurrentDir();
   testShouldSucceedWithSourcePlatformExecutable(); /// 00: ok
-  withTempDir(testExeSymLinked); /// 01: ok
+  // dart:io does not support linking to files in Windows.
+  if (!Platform.isWindows) {
+    withTempDir(testExeSymLinked); /// 01: ok
+  }
   withTempDir(testExeDirSymLinked); /// 02: ok
   testPathToSDKDir(); /// 03: ok
   withTempDir(testPathPointsToSymLinkedSDKPath); /// 04: ok
-  withTempDir(testPathToDirWithExeSymLinked); /// 05: ok
+  // dart:io does not support linking to files in Windows.
+  if (!Platform.isWindows) {
+    withTempDir(testPathToDirWithExeSymLinked); /// 05: ok
+  }
   testShouldSucceedWithEmptyPathEnvironment(); /// 06: ok
 }