found via `pre-commit try-repo https://github.com/codespell-project/codespell --all-files`

Paths specified in configuration files should be relative to the
directory where the configuration file resides.  Formerly, paths were
normalized relative to the current working directory where `flake8` was
invoked.  The former behavior was not expected, especially for directory
structures with subprojects each having their own configuration.

Preemptively determine the path of the user configuration file during
the construction of the `ConfigFileFinder` object.  The user
configuration path will always be the same, regardless of when it gets
obtained by a run of `flake8`.

This isolates the logic of determining the user configuration path into
a static helper method to be called to set the `.user_config_file`
attribute.  The helper method leverages `utils.is_windows()`, instead of
reimplementing the check, and decomposes clearly the directory name and
the base name to construct the path with a single `return` path.
Additionally, this avoids reconstructing the path on demand of obtaining
the user configuration file path.

Remove the checks to see if a configuration file has already been seen
and parsed.  These checks aren't necessary because the entire run of
`flake8` calls these methods *only* once per configuration provided.