text: Title: Regression: specifying workdir is treated like root
  Body: In https://github.com/pypa/twine/issues/684#issuecomment-1350361116, we learned that since tox 4, invoking tox from a tox environment fails to create the environment. Here's a minimal reproducer:
  
  ```
   draft $ cat > tox.ini
  [testenv:parent]
  deps=tox
  allowlist_externals=ls
  commands=
  	python -m tox -e child --notest
  	ls .tox/child
  
  [testenv:child]
   draft $ tox -e parent
  parent: commands[0]> python -m tox -e child
    child: OK (0.02 seconds)
    congratulations :) (0.05 seconds)
  parent: commands[1]> ls .tox/child
  ls: .tox/child: No such file or directory
  parent: exit 1 (0.01 seconds) /Users/jaraco/draft> ls .tox/child pid=69335
    parent: FAIL code 1 (0.18=setup[0.02]+cmd[0.15,0.01] seconds)
    evaluation failed :( (0.21 seconds)
  ```
  
  I suspect one or more of the environment variables supplied in the parent env are affecting the invocation of tox and preventing the child env from being created.