The reason why I added the dependencies to the groovy-all.jar was that I wanted to generate Groovydoc of my Keywords, as I described at How to generate Groovydoc of Plugin
The groovydoc task seems to require groovy-all.jar in the dependecies declaration, so I added it.
Now I enountered a conflict: Katalon-gradle-plugin does not like groovy-all.jar in the dependencies, on the other hand groovydoc task wants it.
May be I can create another build.gradle file for groovydoc task. Even better, the root build.gradle should be designed to support multi projects: one child project is to build Katlaon plugins, other child project is for user’s custom requirements.