bz-63827 Print out stacktrace in "legacy-xml" when the test is aborted too

src/main/org/apache/tools/ant/taskdefs/optional/junitlauncher/LegacyXmlResultFormatter.java

@@ -302,6 +302,8 @@ class LegacyXmlResultFormatter extends AbstractJUnitResultFormatter implements T
                     writer.writeAttribute(ATTR_MESSAGE, message);
                 }
                 writer.writeAttribute(ATTR_TYPE, t.getClass().getName());
+                // write out the stacktrace
+                writer.writeCData(StringUtils.getStackTrace(cause.get()));
             }
             writer.writeEndElement();
         }