custom_rules.xml

<?xml version="1.0" encoding="UTF-8"?>
<project>

    <target name="rename-release-with-version-number" >

        <xmlproperty
            collapseAttributes="true"
            file="AndroidManifest.xml"
            prefix="themanifest" />

        <property
            name="out.packaged.file"
            location="${out.absolute.dir}/${ant.project.name}-${themanifest.manifest.android:versionName}-unsigned.apk" />

        <property
            name="out.final.file"
            location="${out.absolute.dir}/${ant.project.name}-${themanifest.manifest.android:versionName}.apk" />
    </target>

    <target
        name="-set-release-mode"
        depends="rename-release-with-version-number,android_rules.-set-release-mode" >

        <echo message="target: ${build.target}" >
        </echo>
    </target>

</project>