How to lowercase all files with a mapper?

[BCT Roel de Wildt]

Hello,

I have a build script in Apache Ant that is using the following definition to 
move all files from one directory to another directory while everything must be 
lowercase. But the scriptmapper gives a warning in openjdk 11 during the move 
of every file.

Warning:
[move] Warning: Nashorn engine is planned to be removed from a future JDK 
release

Build.xml:

            <target name="compose.default.lower">
                        <mkdir dir="output/rcode/${platform}/${project}" />

                        <move todir="output/rcode/${platform}/${project}">
                                    <fileset 
dir="preproces/rcode/${platform}/${project}">
                                               <include name="**" />
                                    </fileset>
                                    <scriptmapper language="javascript">
                                               self.clear();
                                               
self.addMappedName(source.toLowerCase());
                                    </scriptmapper>
                        </move>
            </target>

Is there a alternative mapper that does not give a warning and could lower case 
everything in the string?

Kind regards,

Roel de Wildt