internetarchive: Provide setuptools at runtime

Since commit f7e28bf5 ("Split
buildPythonPackage into setup hooks"), the `ia` command provided by this
package has crashed with the error:

    Traceback (most recent call last):
      File "/nix/store/7n1jf081h0qnj82m2s69mxzj02zf746f-python3.7-internetarchive-1.8.1/bin/.ia-wrapped", line 7, in <module>
        from internetarchive.cli.ia import main
      File "/nix/store/7n1jf081h0qnj82m2s69mxzj02zf746f-python3.7-internetarchive-1.8.1/lib/python3.7/site-packages/internetarchive/cli/__init__.py", line 27, in <module>
        from internetarchive.cli import ia, ia_configure, ia_delete, ia_download, ia_list, \
      File "/nix/store/7n1jf081h0qnj82m2s69mxzj02zf746f-python3.7-internetarchive-1.8.1/lib/python3.7/site-packages/internetarchive/cli/ia.py", line 60, in <module>
        from pkg_resources import iter_entry_points, DistributionNotFound
    ModuleNotFoundError: No module named 'pkg_resources'

This commit fixes that by adding `setuptools` (which contains the
'pkg_resources' module) to `propagatedBuildInputs`.