protected function getSystem()
    {
        $osName = strtolower(php_uname());

        if ($this->contains($osName, 'darwin')) {
            return 'macosx';
        } elseif ($this->contains($osName, 'win')) {
            return 'windows';
        } elseif ($this->contains($osName, 'linux')) {
            return PHP_INT_SIZE === 4 ? 'linux-i686' : 'linux-x86_64';
        } else {
            throw new RuntimeException('Unknown operating system.');
        }
    }