Individual distributions for Gradle multi-project

I have a number of very similar (non-Java) projects that needs to generate Zip/Tar distribution. Generally each project simply has a distributions section that copies various files/directories and assembles the archive. I would like to extract common code to the separate “common” project but perform the build from the child project(s) so I can generate one archive based on the flavor I need. The common code is simply a directory(s) that need to be included into archive(s)
I probably will never run a build from the parent to generate multiple distributions.
I need to copy common files first and then add/overwrite files from the child project. I looked at examples from samples/userguide/multiproject and would like to use a flat structure. But these examples are pretty spartan so any examples would be greatly appreciated!

To sweeten the deal - I have posted same questions to Stackoverflow with 200 points bounty, feel free to answer there and claim the prize