Fix maven BuildIT failures

extensions/jaxb/deployment/src/main/java/io/quarkus/jaxb/deployment/JaxbProcessor.java

@@ -313,8 +313,11 @@ void setupJaxbContextConfig(JaxbConfig config,
 
         // parse class names to class
         Set<Class<?>> classes = getAllClassesFromClassNames(classNamesToBeBound);
-        // validate the context to fail at build time if it's not valid
-        validateContext(classes);
+        if (config.validateJaxbContext) {
+            // validate the context to fail at build time if it's not valid
+            validateContext(classes);
+        }
+
         // register the classes to be used at runtime
         jaxbContextConfig.addClassesToBeBound(classes);
     }

extensions/jaxb/runtime/src/main/java/io/quarkus/jaxb/runtime/JaxbConfig.java

@@ -9,6 +9,13 @@
 
 @ConfigRoot(phase = ConfigPhase.BUILD_AND_RUN_TIME_FIXED, name = "jaxb")
 public class JaxbConfig {
+
+    /**
+     * If enabled, it will validate the default JAXB context at build time.
+     */
+    @ConfigItem(defaultValue = "true")
+    public boolean validateJaxbContext;
+
     /**
      * Exclude classes to automatically be bound to the default JAXB context.
      */

integration-tests/maven/src/test/resources-filtered/projects/classloader-linkage-error/src/main/resources/application.properties

@@ -1 +1,5 @@
 quarkus.class-loading.parent-first-artifacts=stax:stax-api
+# The dependency `stax-api` is not compatible with the dependency `quarkus-jaxb` because both add the same
+# type `javax.xml.namespace.QName`. This was done on purpose to validate the `parent-first-artifacts` property when building
+# projects with conflicts with Maven, so we need to skip the JaxbContext validation at build time.
+quarkus.jaxb.validate-jaxb-context=false