Fix issue with fast-jar not working using OpenShift and Docker strategy

Fixes quarkusio#16113

(cherry picked from commit df695f3)

extensions/container-image/container-image-openshift/deployment/src/main/java/io/quarkus/container/image/openshift/deployment/OpenshiftProcessor.java

@@ -2,6 +2,7 @@
 
 import static io.quarkus.container.image.openshift.deployment.OpenshiftUtils.mergeConfig;
 import static io.quarkus.container.util.PathsUtil.findMainSourcesRoot;
+import static io.quarkus.deployment.pkg.steps.JarResultBuildStep.DEFAULT_FAST_JAR_DIRECTORY_NAME;
 
 import java.io.BufferedReader;
 import java.io.ByteArrayInputStream;
@@ -252,7 +253,8 @@ public void openshiftBuildFromJar(OpenshiftConfig openshiftConfig,
         //The contextRoot is where inside the tarball we will add the jars. A null value means everything will be added under '/' while "target" means everything will be added under '/target'.
         //For docker kind of builds where we use instructions like: `COPY target/*.jar /deployments` it using '/target' is a requirement.
         //For s2i kind of builds where jars are expected directly in the '/' we have to use null.
-        String contextRoot = config.buildStrategy == BuildStrategy.DOCKER ? "target" : null;
+        String outputDirName = out.getOutputDirectory().getFileName().toString();
+        String contextRoot = getContextRoot(outputDirName, packageConfig.isFastJar(), config.buildStrategy);
         if (packageConfig.isFastJar()) {
             createContainerImage(kubernetesClient, openshiftYml.get(), config, contextRoot, jar.getPath().getParent(),
                     jar.getPath().getParent());
@@ -266,6 +268,16 @@ public void openshiftBuildFromJar(OpenshiftConfig openshiftConfig,
         artifactResultProducer.produce(new ArtifactResultBuildItem(null, "jar-container", Collections.emptyMap()));
     }
 
+    private String getContextRoot(String outputDirName, boolean isFastJar, BuildStrategy buildStrategy) {
+        if (buildStrategy != BuildStrategy.DOCKER) {
+            return null;
+        }
+        if (!isFastJar) {
+            return outputDirName;
+        }
+        return outputDirName + "/" + DEFAULT_FAST_JAR_DIRECTORY_NAME;
+    }
+
     @BuildStep(onlyIf = { IsNormalNotRemoteDev.class, OpenshiftBuild.class, NativeBuild.class })
     public void openshiftBuildFromNative(OpenshiftConfig openshiftConfig, S2iConfig s2iConfig,
             ContainerImageConfig containerImageConfig,