[enhancement] Use the --use-pep517 option in bootstrap.sh

[vkarak]

This is to avoid deprecation warnings from dependencies that are not yet updated (see ClusterShell):

  DEPRECATION: Building 'ClusterShell' using the legacy setup.py bdist_wheel mechanism, which will be removed in a future version. pip 25.3 will enforce this behaviour change. A possible replacement is to use the standardized build interface by setting the `--use-pep517` option, (possibly combined with `--no-build-isolation`), or adding a `pyproject.toml` file to the source tree of 'ClusterShell'. Discussion can be found at https://github.com/pypa/pip/issues/6334

This is a follow up from #3470.