Upgrade to Groovy 2.4.21, fix unsupported target MODULE error.

[dblock]

Groovy 2.4.12 implemented support for target MODULE, whatever that means. Upgraded to the latest version of Groovy 2.4. Added JDK 11 (LTS) to CI.

Had to make two other changes:

• a unit test executed in a, what seems to be, correct order
• calling getResource in @BeforeClass returns null, moved that initialization code in a before block

Fixes #292.

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[nre-ableton]

Last I checked, Jenkins still shipped with Groovy 2.4.12. I'm not sure how I'd feel about updating to a version that is newer than what Jenkins has. Can we just update to 2.4.12? (Which arguably should be done anyways). Would that fix the gradle error?

[dblock]

Well, 2.4.12 doesn't work because it has another bug.

com.lesfurets.jenkins.TestSerializationCPS > testSerialization FAILED
    java.lang.annotation.AnnotationFormatError: Duplicate annotation for class: interface com.cloudbees.groovy.cps.WorkflowTransformed: @com.cloudbees.groovy.cps.WorkflowTransformed()
        at java.base/sun.reflect.annotation.AnnotationParser.parseAnnotations2(AnnotationParser.java:126)
        at java.base/sun.reflect.annotation.AnnotationParser.parseAnnotations(AnnotationParser.java:73)
        at java.base/java.lang.Class.createAnnotationData(Class.java:3757)

The error gets better in 2.4.13.

com.lesfurets.jenkins.TestSerializationCPS > testSerialization FAILED
    org.codehaus.groovy.control.MultipleCompilationErrorsException: startup failed:
    file:/Users/dblock/source/JenkinsPipelineUnit/dblock/src/test/jenkins/job/serializeCPS.jenkins: -1: Annotation @com.cloudbees.groovy.cps.WorkflowTransformed has RUNTIME retention and 2 occurrences. Duplicate annotations not allowed.
     @ line -1, column -1.
    1 error

It goes away in 2.4.14.

Best I can do to 2.4.12 is 2.4.14, but maybe we want go to the latest patch release, because this is not a runtime library? I would want to see a test that passes here and fails in Jenkins because of Groovy version. I could easily have the same argument across Java versions - we build using Java 8, but I run tests with Java 11 in my own project.

[nre-ableton]

I guess 2.4.14 is "close enough" to 2.4.12. 😅 It would be nice if you squashed b2d3362 and 056df8b, as 056df8b doesn't really do much except get blown away by the next commit. However, that's just a minor nitpick. Thanks for all of your work on this PR.

[dblock]

I guess 2.4.14 is "close enough" to 2.4.12. 😅 It would be nice if you squashed b2d3362 and 056df8b, as 056df8b doesn't really do much except get blown away by the next commit. However, that's just a minor nitpick. Thanks for all of your work on this PR.

Squashed.