The commands provided to generate dependency tarballs in go-module.eclass produce tarballs with duplicate files, that are much larger than they need to be. The `go-mod` directory ends up containing a `cache` subdirectory that includes downloaded .zip archives of Go packages, and other subdirectories containing the same packages unpacked from these .zip archives. Not only is the data duplicated — but since one copy is deflate-compressed, they end up being compressed inefficiently. If I removed all .zip files, go-module.eclass seems to be able to build, test and install the package without issue. Not sure which other files can be removed. For app-misc/siegfried-1.11.0, the archive is almost 2.5x smaller: original command: 31M after removing .zip files: 13M
