There can be many ways to create a jar file.
The first link shows an example how groovy is compiled.
groovyc Sample.groovy
From the posts, customScripts is a directory under which all groovy scripts are available in the development environment.
If so, then go to customScripts directory, and run groovyc *.groovy, add -cp <additional libs> as needed.
Now come out of customScripts directory, run command
jar -cvf customscripts.jar customScripts/*.class
Once jar is created, try to open it and see all the classes appear under customScripts.
Hope this helps.
