This tool is for generating small tarballs for large Zig monorepos.
The other usecase for this tool is for out-of-source build.zig packaging for
C/C++ libraries. Ideally one would have the C library as a git submodule, but
submodules are not included in GitHub's archive API so people tend to fork
these libraries and add a build.zig to get the archive API for free. There are
ups and downs to either direction, and this tool tries to level the convenience
by bundling the submodule source for you.