It seems `$ORIGIN` resolves prior to symlink resolution. This makes it
resolve
differently depending on if the directory or file itself is symlinked.

To fix, special case shared libraries and have them symlinked directly.
Since an
explicit file is the target, `VenvSymlinkEntry.link_to_file` is added to
hold the
File object that will be linked to.

An unfortunate side-effect of this logic is any package with `lib*.so`
files
will be more expensive to build (depset flattened at analysis time, more
files
symlinked), but it beats not working at all. Optimizing that can be done
in
another change.

Tests added to generate libraries that look like what something from
PyPI
does. Manually verified a case using jax and jax plugins.

Fixes #3228