Ant Classloader task and java 13

Question

I'm upgrading our app from Java 8 to Java 13. We use Eclipse ECJ in our build process. To make it work, our ant script has:

    <taskdef resource="net/jtools/classloadertask/antlib.xml" classpath="${build-helpers-lib.dir}/ant-classloadertask.jar" />
    <classloader loader="project" classpath="${build-helpers-lib.dir}/ecj-4.13.jar" />

This fails when Ant is running under Java 13 with this error:

15:50:06  classloader: started Tue Dec 10 15:50:06 PST 2019
15:50:06  WARNING: An illegal reflective access operation has occurred
15:50:06  WARNING: Illegal reflective access by org.apache.tools.ant.taskdefs.classloader.adapter.URLClassLoaderAdapter (file:/home/jenkins/jenkins/workspace/Metrix_2020_1/Metrix-AutomatedBuild/lib/ant-classloadertask.jar) to method java.net.URLClassLoader.addURL(java.net.URL)
15:50:06  WARNING: Please consider reporting this to the maintainers of org.apache.tools.ant.taskdefs.classloader.adapter.URLClassLoaderAdapter
15:50:06  WARNING: Use --illegal-access=warn to enable warnings of further illegal reflective access operations
15:50:06  WARNING: All illegal access operations will be denied in a future release
15:50:06  
15:50:06  classloader: finished Tue Dec 10 15:50:06 PST 2019 (57)
15:50:06  
15:50:06  BUILD FAILED

Any suggestions for a workaround?