Failing joint build

[Paolo Di Tommaso]

Daer maintainers,

The Nextflow joint build
<http://ci.groovy-lang.org/project.html?projectId=JointBuilds_Nextflow&tab=projectOverview>
is failing with this error message.

System.getenv('CI_GROOVY_VERSION') == GroovySystem.getVersion()
       |                           |               |
       2.5.6-SNAPSHOT              |               2.5.5
                                   false
                                   10 differences (28% similarity)
                                   2.5.(6-SNAPSHOT)
                                   2.5.(5---------)


It looks the Groovy runtime version is not matching the declared version by
the `CI_GROOVY_VERSION` env var.

Could you please give it a look.


Cheers,
Paolo