Don't pull jars from parent classloader for "gradle doc". Fixes #9074

Author: graemerocher

grails-gradle-plugin/src/main/groovy/org/grails/gradle/plugin/doc/PublishGuideTask.groovy

@@ -63,7 +63,8 @@ class PublishGuideTask extends AbstractCompile {
     @TaskAction
     protected void compile() {
         def urls = getClasspath().files.collect() { File f -> f.toURI().toURL() }
-        def classLoader = new URLClassLoader(urls as URL[])
+
+        def classLoader = new URLClassLoader(urls as URL[], (ClassLoader) null)
         def docPublisher = classLoader.loadClass("grails.doc.DocPublisher").newInstance(srcDir, destinationDir, project.logger)
         if(groovydocDir?.exists()) {
             project.copy {