Updated path resolution for symlinks

I wanted to symlink the file in vendor/bin to an other folder and `__DIR__` was resolved to this new folder.

by adding `realpath` it resolves the symlink and works again.

Author: onigoetz

composer/bin/phpunit

@@ -38,8 +38,8 @@
 define('PHPUnit_MAIN_METHOD', 'PHPUnit_TextUI_Command::main');
 
 $files = array(
-  __DIR__ . '/../../vendor/autoload.php',
-  __DIR__ . '/../../../../autoload.php'
+  realpath(__DIR__) . '/../../vendor/autoload.php',
+  realpath(__DIR__) . '/../../../../autoload.php'
 );
 
 foreach ($files as $file) {