Fix - normalize cwd path on dist path check (#4088)

[spxd]

Summary of changes

Normalize CWD path for the comparing of distribute location.

Fixes #4088

Pull Request Checklist

• Changes have tests
• News fragment added in newsfragments/.
  (See documentation for details)

[abravalheri]

@spxd thank you very much for the contribution.

The CI is currently complaining that the lines setuptools/command/easy_install.py 1253-1254,1259-1260 were changed but that the changes are not covered in tests (I understand that they probably were not covered before, but since this PR modifies them it would be important to add tests against regression).

Would it be possible to add a test for the update_pth function as well to cover those lines? (I believe that line 1288 can be ignored since it is setuptools-specific).