"Could not find or load main class org.opengts.util.CompiletimeVars" error with Ant

Question

I am working on OpenGTS and I am trying to compile it using build.xml with the command ant all. I keep on getting this error:

[java] Error: Could not find or load main class org.opengts.util.CompiletimeVars

Java returned: 1

Code:

<!-- (re)create compile time source file here? -->
<echo message="Creating CompileTime module ..."/>
<java classname="org.opengts.util.CompiletimeVars" fork="true" failonerror="true">
    <arg value="-configFileDir=${basedir}"/>
    <arg value="-template?=${basedir}/CompileTime.jtemp"/>
    <arg value="-package=org.opengts"/>
    <arg value="-output=${src.gts}/org/opengts/CompileTime.java"/>
    <arg value="-overwrite=false"/> <!-- do not overwrite -->
    <arg value="-extra=${CompiletimeVars.extra}"/>
    <arg value="${CompiletimeVars.arg}"/>
    <arg value="${CompiletimeVars.arg.1}"/>
    <arg value="${CompiletimeVars.arg.2}"/>
    <arg value="${CompiletimeVars.arg.3}"/>
    <classpath>
        <pathelement location="${build.lib}/gtsutils.jar"/>
    </classpath>
</java>