it seems to come from this JAR:

Archive:  out/target/common/obj/JAVA_LIBRARIES/apache-xml_intermediates/classes-full-debug.jar
  Length      Date    Time    Name
---------  ---------- -----   ----
        0  02-19-2020 21:21   META-INF/
       61  02-19-2020 21:21   META-INF/MANIFEST.MF
     4999  02-19-2020 16:17   org/apache/xalan/Version.src
     4126  02-19-2020 16:17   org/apache/xalan/processor/XSLProcessorVersion.src
     1061  02-19-2020 16:17   org/apache/xalan/res/XSLTInfo.properties
    11338  02-19-2020 16:17   org/apache/xml/serializer/Encodings.properties
     4353  02-19-2020 16:17   org/apache/xml/serializer/HTMLEntities.properties
     4720  02-19-2020 16:17   org/apache/xml/serializer/Version.src
     1086  02-19-2020 16:17   org/apache/xml/serializer/XMLEntities.properties
     1841  02-19-2020 16:17   org/apache/xml/serializer/output_html.properties
     1525  02-19-2020 16:17   org/apache/xml/serializer/output_text.properties
     1769  02-19-2020 16:17   org/apache/xml/serializer/output_unknown.properties
     1818  02-19-2020 16:17   org/apache/xml/serializer/output_xml.properties
---------                     -------
    38697                     13 files

As this file is called "classes-full", I wonder whether this is already incomplete (due to the lack of any class..)?