Don't run Kubernetes manifest generation in tests

In tests, various Build Items are population with the
proper values (like the output target), so it's best
to not run the Kubernetes manifest generation at all
in order to avoid getting NPEs

Fixes: quarkusio#15555

extensions/kubernetes/vanilla/deployment/src/main/java/io/quarkus/kubernetes/deployment/KubernetesProcessor.java

@@ -17,6 +17,7 @@
 import java.util.Set;
 import java.util.stream.Collectors;
 
+import io.quarkus.deployment.IsTest;
 import org.jboss.logging.Logger;
 
 import io.dekorate.Session;
@@ -75,7 +76,7 @@ public EnabledKubernetesDeploymentTargetsBuildItem enabledKubernetesDeploymentTa
         return new EnabledKubernetesDeploymentTargetsBuildItem(entries);
     }
 
-    @BuildStep
+    @BuildStep(onlyIfNot = IsTest.class)
     public void build(ApplicationInfoBuildItem applicationInfo,
             OutputTargetBuildItem outputTarget,
             PackageConfig packageConfig,