Autoloader broken for packages using target-dir

[derhasi]

Currently packages, that utilise target-dir are not correctly installed. The autoloader will break for those.

How to reproduce

composer.json:

{
  "name": "derhasi/composer-test",
  "minimum-stability": "dev",
  "prefer-stable": true,
  "require": {
    "davidbarratt/custom-installer": "dev-master",
    "symfony/console": "2.3.*"
  },
  "config": {
    "vendor-dir": "vendor"
  },
  "extra": {
    "custom-installer": {
      "library": "vendor/{$vendor}/{$name}"
    }
  }
}

After composer install the following autoloader is generated at vendor/composer/autoload_namespaces.php:

<?php

// autoload_namespaces.php @generated by Composer

$vendorDir = dirname(dirname(__FILE__));
$baseDir = dirname($vendorDir);

return array(
    'Symfony\\Component\\Console\\' => array($baseDir . '/'),
);

But it should be 'Symfony\\Component\\Console\\' => array($vendorDir . '/symfony/console'), instead.

[davidbarratt]

Fixed per #6