How to handle a "fat source" (multiple sources contained in a single tar file)?

Hello, Nixers!

I am retaking my TDE on NixOS project. A thing worth mentioning is that they provide the sources of each and every library as a self-contained, traditional .tar.gz file, but they also provide a huge .tar file containing all these same .tar.gz files.

Then we have a choice here: download every file separatedly, or download the huge one and untar it. The end result is the same: 150+ sources.

How can I handle this? Download a huge file, generate multiple outputs and use them as inputs/sources for other expressions?

Here is a link for the most recent release.