I was trying to make use of the IzPack installer with Spark 2.7.2 and IzPack 5.0.5 on Windows 8.1 (64-bit).
It didn’t work. So I hacked on the build.xml file and changed the appropriate section.
Please Consider this an informal patch (In other words: Change the related section of your build/build.xml file [line: 890+]):
<target name="installer.izpack" depends="exe" description="build release a izpack installer">
<taskdef name=“IzPack”
classpathref=“build.classpath”
classname=“com.izforge.izpack.ant.IzPackTask”/>
<IzPack input="${basedir}/build/installer/spark-izpack.xml" output="${basedir}/installer/spark-installer.jar"
installerType=“standard” izPackDir="${installer.izpack.dir}" basedir="${basedir}"/>
</target>
…Then it should work!