build.xml

<?xml version="1.0" encoding="UTF-8"?>
<project name="object-enumerator">
    <target name="clean" description="Cleanup build artifacts">
        <delete dir="${basedir}/vendor"/>
        <delete file="${basedir}/composer.lock"/>
    </target>

    <target name="composer" depends="clean" description="Install dependencies with Composer">
        <tstamp>
            <format property="thirty.days.ago" pattern="MM/dd/yyyy hh:mm aa" offset="-30" unit="day"/>
        </tstamp>
        <delete>
            <fileset dir="${basedir}">
                <include name="composer.phar"/>
                <date datetime="${thirty.days.ago}" when="before"/>
            </fileset>
        </delete>

        <get src="https://getcomposer.org/composer.phar" dest="${basedir}/composer.phar" skipexisting="true"/>

        <exec executable="php">
            <arg value="composer.phar"/>
            <arg value="install"/>
        </exec>
    </target>
</project>