Source tarballs are not very useful anymore. People who want to build
from source can also just build from the Git repository. Once upon a
time, the source tarball also saved users from needing a few
dependencies (e.g. bison and flex) but those are dwarfed by the other
dependencies, so it's no longer worth it.

Note: the release script should be updated to copy the vendoredCrates
tarball.