How to call for a Maven goal within an Ant script?

Since none of the solutions worked for me, this is what I came up with:

Assuming you are running on Windows:

<target name="mvn">
    <exec dir="." executable="cmd">
        <arg line="/c mvn clean install" />
    </exec>
</target>

or on UNIX:

<target name="mvn">
    <exec dir="." executable="sh">
        <arg line="-c 'mvn clean install'" />
    </exec>
</target>

or if you want it to work on both UNIX and Windows:

<condition property="isWindows">
    <os family="windows" />
</condition>

<condition property="isUnix">
    <os family="unix" />
</condition>

<target name="all" depends="mvn_windows, mvn_unix"/>

<target name="mvn_windows" if="isWindows">
    <exec dir="." executable="cmd">
        <arg line="/c mvn clean install" />
    </exec>
</target>

<target name="mvn_unix" if="isUnix">
    <exec dir="." executable="sh">
        <arg line="-c 'mvn clean install'" />
    </exec>
</target>