Gradle Plugin is only compatible with JDK 21

[wba2hi]

Trying to build an app on JDK 17 or below leads to the following message:

A problem occurred configuring project ':app'.
> Could not resolve all artifacts for configuration ':app:classpath'.
   > Could not resolve org.eclipse.velocitas:vss-processor-plugin:0.1.1.
     Required by:
         project :app > org.eclipse.velocitas.vss-processor-plugin:org.eclipse.velocitas.vss-processor-plugin.gradle.plugin:0.1.1
10 actionable tasks: 10 executed
Configuration cache entry stored.
      > No matching variant of org.eclipse.velocitas:vss-processor-plugin:0.1.1 was found. The consumer was configured to find a library for use during runtime, compatible with Java 17, packaged as a jar, and its dependencies declared externally, as well as attribute 'org.gradle.plugin.api-version' with value '8.7' but:
          - Variant 'apiElements' declares a library, packaged as a jar, and its dependencies declared externally:
              - Incompatible because this component declares a component for use during compile-time, compatible with Java 21 and the consumer needed a component for use during runtime, compatible with Java 17
              - Other compatible attribute:
                  - Doesn't say anything about org.gradle.plugin.api-version (required '8.7')
          - Variant 'javadocElements' declares a component for use during runtime, and its dependencies declared externally:
              - Incompatible because this component declares documentation and the consumer needed a library
              - Other compatible attributes:
                  - Doesn't say anything about its elements (required them packaged as a jar)
                  - Doesn't say anything about its target Java version (required compatibility with Java 17)
                  - Doesn't say anything about org.gradle.plugin.api-version (required '8.7')
          - Variant 'runtimeElements' declares a library for use during runtime, packaged as a jar, and its dependencies declared externally:
              - Incompatible because this component declares a component, compatible with Java 21 and the consumer needed a component, compatible with Java 17
              - Other compatible attribute:
                  - Doesn't say anything about org.gradle.plugin.api-version (required '8.7')
          - Variant 'sourcesElements' declares a component for use during runtime, and its dependencies declared externally:
              - Incompatible because this component declares documentation and the consumer needed a library
              - Other compatible attributes:
                  - Doesn't say anything about its elements (required them packaged as a jar)
                  - Doesn't say anything about its target Java version (required compatibility with Java 17)
                  - Doesn't say anything about org.gradle.plugin.api-version (required '8.7')

Since we can not find here source- and targetCompatibility options the solution is probably to simply add the following lines to build.gradle.kts:

java {
    sourceCompatibility = JavaVersion.VERSION_11
    targetCompatibility = JavaVersion.VERSION_11
}

kotlin {
    compilerOptions {
        jvmTarget.set(JvmTarget.JVM_11)
    }
}