Install fails with --use-pep517

[mklim]

Thanks for maintaining this project. The flag ends up being a problem because poetry calls --use-pep517 when installing dependencies. (python-poetry/poetry#3433)

Steps to reproduce

$ mkdir /tmp/repro \
      && cd /tmp/repro \
      && python3 -m venv .venv \
      && source .venv/bin/activate
$ pip install --use-pep517 py_stringmatching
Collecting py_stringmatching
  Using cached py_stringmatching-0.4.2.tar.gz (661 kB)
  Installing build dependencies ... done
  Getting requirements to build wheel ... error
  error: subprocess-exited-with-error

  × Getting requirements to build wheel did not run successfully.
  │ exit code: 1
  ╰─> [17 lines of output]
      Traceback (most recent call last):
        File "/private/tmp/repro/.venv/lib/python3.9/site-packages/pip/_vendor/pep517/in_process/_in_process.py", line 363, in <module>
          main()
        File "/private/tmp/repro/.venv/lib/python3.9/site-packages/pip/_vendor/pep517/in_process/_in_process.py", line 345, in main
          json_out['return_val'] = hook(**hook_input['kwargs'])
        File "/private/tmp/repro/.venv/lib/python3.9/site-packages/pip/_vendor/pep517/in_process/_in_process.py", line 130, in get_requires_for_build_wheel
          return hook(config_settings)
        File "/private/var/folders/vf/5h145x1d77b5vm70kq4xcnj80000gn/T/pip-build-env-e7h9dqmw/overlay/lib/python3.9/site-packages/setuptools/build_meta.py", line 338, in get_requires_for_build_wheel
          return self._get_build_requires(config_settings, requirements=['wheel'])
        File "/private/var/folders/vf/5h145x1d77b5vm70kq4xcnj80000gn/T/pip-build-env-e7h9dqmw/overlay/lib/python3.9/site-packages/setuptools/build_meta.py", line 320, in _get_build_requires
          self.run_setup()
        File "/private/var/folders/vf/5h145x1d77b5vm70kq4xcnj80000gn/T/pip-build-env-e7h9dqmw/overlay/lib/python3.9/site-packages/setuptools/build_meta.py", line 483, in run_setup
          super(_BuildMetaLegacyBackend,
        File "/private/var/folders/vf/5h145x1d77b5vm70kq4xcnj80000gn/T/pip-build-env-e7h9dqmw/overlay/lib/python3.9/site-packages/setuptools/build_meta.py", line 335, in run_setup
          exec(code, locals())
        File "<string>", line 14, in <module>
      ImportError: pip is not installed.
      [end of output]

  note: This error originates from a subprocess, and is likely not a problem with pip.
error: subprocess-exited-with-error

× Getting requirements to build wheel did not run successfully.
│ exit code: 1
╰─> See above for output.

note: This error originates from a subprocess, and is likely not a problem with pip.