Gradle project dependency problems

Question

I have a multi-project Gradle build that is configured as this:

keycloak
|-- keycloak-spi-1
|-- keycloak-spi-2
|-- keycloak-theme

the subprojects build jars that i want to include inside docker that is build in the parent with Jib but, an error message appears: Obtaining project build output files failed

Gradle is version 7.4.1

Thanks

---

After some investigation, Jib use the output of jar task during the image build and, in this case, jar task must not compile sources but copy the shadowJars from all the subprojects. I take this approach but not work:

task jar(type: Jar, overwrite: true) {
    subprojects {
        from(tasks.shadowJar)
    }
    into "${buildDir}/libs"
    doLast {
        delete jar.archiveFile
    }
}