COMPOSER_ROOT_VERSION doesn't modify the version within composer.json of archive.

````
$ cat composer.json 
{
    "name": "wackka/waccka",
    "version": "0.1",

    "repositories": [
        {
            "type": "artifact",
            "url": "sandbox/"
        }
    ],
    "require": {
        "blurps/ormie": "*",
        "doctrine/orm": "2.3.3"
    }
}
$ cd composer/; COMPOSER_ROOT_VERSION=23.0.2 ROOT_PACKAGE_VERSION=22.0.1 composer.phar archive --format=zip; mv composer-composer-23.0.2.zip ../sandbox; cd ..; ./local-composer-link install -v --dry-run
....
Creating the archive.
Loading composer repositories with package information
File .DS_Store doesn't seem to hold a package
File 2.4.0-BETA1.tar.gz doesn't seem to hold a package
                                                     
  [UnexpectedValueException]                         
  Package composer/composer has no version defined. 
````