Specify source file language in build.xml?

I'm trying to build an Android project from the command line. I'm
getting an error during `ant release`. The error is unmappable
character for encoding UTF-8.

The sources appear to be written by a non-English speaker, and the
offending characters are in comments like so:

    /*
     * Projet   : Permission Explorer
     * Auteur   : Carlo Criniti
     * Date     : 2011.06.10
     *
     * Classe ApplicationDetail
     * ActivitÈ d'affichage du dÈtail d'une application
     * avec les permissions qu'elle utilise
     */

There are multiple errors like this. If /usr/local/bin/ant release
2>&1 | grep -i error | wc -l is accurate, then there's 103 of them.

I've been through ant's documentation at "Writing a Simple Buildfile"
(http://ant.apache.org/manual/using.html) and "Property Task"
(http://ant.apache.org/manual/Tasks/property.html), but damn if I can
figure out how to set a source file language to get past these errors.

How do I specify a source file language in build.xml?