XWIKI-18801: Docker-based tests overriding components failing when the build...

XWIKI-18801: Docker-based tests overriding components failing when the build is executed with the "maven.build.dir" system property

  * Ensure to use the target output directory only if inside a container
    build

(cherry picked from commit 4d98bc81)

xwiki-platform-core/xwiki-platform-test/xwiki-platform-test-docker/src/main/java/org/xwiki/test/docker/internal/junit5/WARBuilder.java

@@ -235,7 +235,11 @@ private int extractJettyVersionFromDockerTag(String tag)
     private void copyClasses(File webInfClassesDirectory, TestConfiguration testConfiguration) throws Exception
     {
         LOGGER.info("Copying resources to WEB-INF/classes ...");
-        File classesDirectory = new File(testConfiguration.getOutputDirectory(), "classes");
+        // if we're building a jetty standalone it means we're using a standard maven build so the classes will be built
+        // in target/classes directly.
+        String outputDirectory = (testConfiguration.getServletEngine() != ServletEngine.JETTY_STANDALONE)
+            ? testConfiguration.getOutputDirectory() : "target";
+        File classesDirectory = new File(outputDirectory, "classes");
         if (classesDirectory.exists()) {
             copyDirectory(classesDirectory, webInfClassesDirectory);
         }