Add alwaysAllowBuildFiles config var to always enable build files in dev...

Hi Mark. 
Here is a quick change to allow build files to be used in development mode. The rationale here is that I usually have a third_party target that includes CSS files from third-party libraries that are *not* likely to change very often (say, Font Awesome, jQuery UI, etc). Having the controller regenerate that target in development mode takes time/resources, I'd rather serve the build file. My own JS/CSS development files, which are likely to change a lot more often, are in a different target, created by the Asset Helper with the 'raw' option set to true in dev mode. TLDR; in dev mode I end up with one link rel="stylesheet" serving all third party CSS, then one link per application-specific css file. In production mode, this automatically defaults to all targets being build files (I.e. only two links). This scenario used to work with the 1.3 version of that plugin. I'm upgrading CakePHP to 2.x, and upgraded that plugin as well; it no longer works. This option brings that "feature" back. 
Thanks
Mark. This would be great, thank you. Unfortunately, this would not work for me specifically, because of a different "issue" I'm having, though it could be easy to fix as well, hopefully you can tell me. The issue is with the CssUrlRewrite filter I'm using. It has one configuration setting, rewriteUrl, but I can't set its value in asset_compress.ini, because it has to change from server to server, or developer to developer (say, if the app is accessed from http:://local.app, or http://local.app/flavor1, the webroot is different in each case). 
In version 1.3 of AssetCompress & CakePHP my ini file has:

    rewriteUrl = DISPATCHER_WEBROOT

i.e. a constant I want AssetCompress to resolve. Unfortunately, nothing in AssetConfig::constantMap can be used (WEBROOT and ROOT are full path), and I was not able to inject additional constants to set DISPATCHER_WEBROOT either, so I had to hack the asset_config.php constructor back then:

    public function __construct(...) {
    [...]
    if (isset($GLOBALS['Dispatcher']))
      {
      $webroot = $GLOBALS['Dispatcher']->webroot;
      $additionalConstants['DISPATCHER_WEBROOT'] = $webroot;
      }
    $this->constantMap = array_merge($this->constantMap, $additionalConstants);

As I mentioned, I'm upgrading our whole code base to CakePHP 2.x, and AssetCompress in the process. In our own compressAsset() method, which regenerate the build files, I'm able to do this now:

    $config = AssetConfig::buildFromIniFile();
    $rewrite_url = Configure::read('App.baseUrl');
    $config->filterConfig('CssUrlRewrite', array('rewriteUrl' => $rewrite_url));

though honestly I don't know if baseUrl is what I need, I haven't tested it on a machine that has a non-empty webroot yet. I need to inject the controller's webroot, without the trailing slash.
Now it is my understanding that the Dispatcher would just read the asset_compress.ini, i.e. I would not be able to inject the proper value for rewriteUrl, and that's why the solution you describe would not work for me. Would be great though. It could be solved, I think, if:
* constantMap included a few more variables (URLs, not paths, say, the webroot, without the last slash),
* or rewriteUrl in the CssRewriteUrl would default to the controller's webroot without the slash (out of your control or mine probably),
* or we could specify additional config files that AssetCompress would read. For example, asset_compress.ini could have something like: 
     localConfigFiles = asset_compress.local.ini

Upon reading the usual .ini file, it would then try to read any localConfigFiles (they don't have to exist) and merge the settings. This would allow local settings to be set per developer or production server (not committed to the code), and I would put the correct value for rewriteUrl there.

I prefer a).

Thanks.