Fix Gradle test not using Java 8

[gsmet]

@glefloch could you have another look at this one? I don't understand why CI didn't catch it and only the release build process job did.

Also I wasn't able to run the test anyway (but I tried to do it from the directory itself by fixing a few properties) so I'm not sure if it's just my setup that is incorrect.

Last error I had was:

Caused by: java.util.NoSuchElementException
        at io.quarkus.deployment.builditem.ArchiveRootBuildItem.<init>(ArchiveRootBuildItem.java:97)
        at io.quarkus.deployment.builditem.ArchiveRootBuildItem.<init>(ArchiveRootBuildItem.java:17)
        at io.quarkus.deployment.builditem.ArchiveRootBuildItem$Builder.build(ArchiveRootBuildItem.java:50)
        at io.quarkus.deployment.QuarkusAugmentor.run(QuarkusAugmentor.java:141)
        at io.quarkus.runner.bootstrap.AugmentActionImpl.runAugment(AugmentActionImpl.java:394)

Is there an easy way to only run one Gradle test?

[glefloch]

@gsmet good catch!

I think the gradle CI runs only with java 11, whereas the release job is using java 8. Maybe we should switch the gradle ci to java 8?

If you only want to run this test, you can do it with;

./gradlew clean test --tests MultiModuleWithEmptyModuleDevModeTest

I'm building quarkus locally to test your fix, I never remember if it's 8 or 1.8 for java version.

[gsmet]

Ah, yes, you're right about us only testing with Java 11.

There's a good chance we will drop Java 8 support very soon so no need to change the workflows.