Concat/Minify JS files using a xml file as list

I have a xml file that has JS lists per module, something like this:

<authentication>
    <files>
        <file>vendor/jquery.scrollTo.js</file>
        <file>vendor/Mustache.js</file>
        <file>plugins/ScrollTo.js</file>
        <file>plugins/FlashMessages.js</file>
        <file>plugins/Validator.js</file>
        <file>attachers/Global.js</file>
    </files>
</authentication>

<index>
    <files>
        <file>vendor/jquery.scrollTo.js</file>
        <file>vendor/Mustache.js</file>
        <file>plugins/ScrollTo.js</file>
        <file>plugins/FlashMessages.js</file>
        <file>plugins/Validator.js</file>
        <file>attachers/Global.js</file>
    </files>
</index>

Now, I want to use this nodes in order to minify and concatenate all into a single file, doing something like following:

<authentication>
    <files>
        <file>vendor/jquery.scrollTo.js</file>
        <file>vendor/Mustache.js</file>
        <file>plugins/ScrollTo.js</file>
        <file>plugins/FlashMessages.js</file>
        <file>plugins/Validator.js</file>
        <file>attachers/Global.js</file>
    </files>
    <target>public/js/authentication.min.js</target>
</authentication>

and i want that authentication.min.js has all concatenated and minified inside.

Does anyone know how i should set up a build.xml file for ant that uses an external xml file as config file?

Thanks in advance!