How to build native Graal image for 21

[erkieh]

I have tried generating a docker image from an empty project with the Micronaut lauch website but when I try to run the gradle task
dockerBuildNative
my
build/docker/native-main/DockerfileNative
first line is

FROM ghcr.io/graalvm/native-image-community:17-ol9 AS graalvm
and I get an error

[1/8] Initializing...                                                                                    (0.0s @ 0.17GB)
Error: Unable to load 'com.native21.ApplicationKt' due to a Java version mismatch.
Please take one of the following actions:
 1) Recompile the source files for your application using Java 17, then try running native-image again
 2) Use a version of native-image corresponding to the version of Java with which you compiled the source files for your application

even though my JAVA_HOME is pointing to 21, gradle is 8.5 and build.gradle has

java {
    sourceCompatibility = JavaVersion.toVersion("21")
    targetCompatibility  = JavaVersion.toVersion("21")
}
tasks.withType<org.jetbrains.kotlin.gradle.tasks.KotlinCompile>().configureEach {
    kotlinOptions {
        jvmTarget = "21"
    }
}

How to configure it correctly?

[erkieh]

I did get it to work by adding this to my build.gradle file:

tasks.withType<NativeImageDockerfile>().configureEach {
    jdkVersion = "21"
}

But is this the intended way to do it?