title: Laravel 7 upgrade failing
body: <p>I was following the Laravel 6.x to Laravel 7.x upgrade doc and made the necessary changes. But it is failing and showing the following error. At the time of running <code>composer update</code> there were not 3rd party packages. Then i installed some other packages and after that tried to update again and stuck at this error.</p>
  
  <pre><code>Generating optimized autoload files
  &gt; Illuminate\Foundation\ComposerScripts::postAutoloadDump
  &gt; @php artisan package:discover --ansi
  PHP Fatal error:  Uncaught TypeError: Argument 1 passed to Symfony\Component\Process\Process::__construct() must be of the type array, string given, called in phar:///usr/local/bin/composer/src/Composer/Util/ProcessExecutor.php on line 65 and defined in /var/www/html/laravel/laravel-starter/vendor/symfony/process/Process.php:140
  Stack trace:
  #0 phar:///usr/local/bin/composer/src/Composer/Util/ProcessExecutor.php(65): Symfony\Component\Process\Process-&gt;__construct(''/usr/bin/php7....', NULL, NULL, NULL, 300)
  #1 phar:///usr/local/bin/composer/src/Composer/EventDispatcher/EventDispatcher.php(245): Composer\Util\ProcessExecutor-&gt;execute(''/usr/bin/php7....')
  #2 phar:///usr/local/bin/composer/src/Composer/EventDispatcher/EventDispatcher.php(96): Composer\EventDispatcher\EventDispatcher-&gt;doDispatch(Object(Composer\Script\Event))
  #3 phar:///usr/local/bin/composer/src/Composer/Autoload/AutoloadGenerator.php(312): Composer\EventDispatcher\EventDispatcher-&gt;dispatchScript('post-autoload-d...', true, Array, Array)
  #4 phar:///usr/local/bin in /var/www/html/laravel/laravel-starter/vendor/symfony/process/Process.php on line 140
  
  Fatal error: Uncaught TypeError: Argument 1 passed to Symfony\Component\Process\Process::__construct() must be of the type array, string given, called in phar:///usr/local/bin/composer/src/Composer/Util/ProcessExecutor.php on line 65 and defined in /var/www/html/laravel/laravel-starter/vendor/symfony/process/Process.php:140
  Stack trace:
  #0 phar:///usr/local/bin/composer/src/Composer/Util/ProcessExecutor.php(65): Symfony\Component\Process\Process-&gt;__construct(''/usr/bin/php7....', NULL, NULL, NULL, 300)
  #1 phar:///usr/local/bin/composer/src/Composer/EventDispatcher/EventDispatcher.php(245): Composer\Util\ProcessExecutor-&gt;execute(''/usr/bin/php7....')
  #2 phar:///usr/local/bin/composer/src/Composer/EventDispatcher/EventDispatcher.php(96): Composer\EventDispatcher\EventDispatcher-&gt;doDispatch(Object(Composer\Script\Event))
  #3 phar:///usr/local/bin/composer/src/Composer/Autoload/AutoloadGenerator.php(312): Composer\EventDispatcher\EventDispatcher-&gt;dispatchScript('post-autoload-d...', true, Array, Array)
  #4 phar:///usr/local/bin in /var/www/html/laravel/laravel-starter/vendor/symfony/process/Process.php on line 140
  
  </code></pre>
  
  <p>Source of the project is available at: <a href="https://github.com/nasirkhan/laravel-starter/tree/v7" rel="nofollow noreferrer">https://github.com/nasirkhan/laravel-starter/tree/v7</a></p>