How can I create jar files from altogether different fileset directory

I do have the following ANT equivalent where I want to generate the same in Gradle.

I have few java sub projects, they build one after another.

  1. project.common build first that produces two custom jars.
  2. project.commands build next that produces another two custom jars.

I have no problem with project.common. The project.commands have problem. The current ANT script of project.command build Jars in such a way that it creates a selective jar from project.common folder.

 <jar jarfile="${dir.lib}/$project.common.jar}" update="no" >
            <fileset dir="${common.classes.dir}" includes="**/*audit/**,**/*debug/**,**/*util*/*.class,**/*Config*.class,**/*exception*/*.class,**/*nls*/**,**/*log4j*/**,**/*credvault*/**" />
            <fileset dir="${dir.common.src}"   includes="com/**/*.properties" />

My gradle script executes from project.commands and that compiles the code. Then next I want to build Jar files where the source of jars are outside this project. How can I create Jar by specifying external file set equivalent without adding sourceSetts.