When using the backtracking resolver, the custom cache dir flag appears to be ignored.

Environment Versions

1. Ubuntu 22.04
2. Python version: 3.11.1
3. pip version: 22.3.1
4. pip-tools version: 6.12.1

Steps to replicate

Execute the command pip-compile -v --cache-dir /tmp/pip-cache --resolver=backtracking --upgrade requirements/requirements.in

Expected result

The cache found in /tmp/pip-cache is used.

Actual result

The default cache folder in ~/.cache/pip-tools is used. No files are generated in /tmp/pip-cache.
Note that without the --resolver=backtracking flag, the cache is properly generated and read from the custom path.