Add RUFF_OUTPUT_FILE environment variable support

[sisp]

Summary

I've added support for configuring the ruff check output file via the environment variable RUFF_OUTPUT_FILE akin to #1731.

This is super useful when, e.g., generating a GitLab code quality report while running Ruff as a pre-commit hook. Usually, ruff check should print its human-readable output to stdout, but when run through pre-commit in a GitLab CI job it should write its output in gitlab format to a file. So, to override these two settings only during CI, environment variables come handy, and RUFF_OUTPUT_FORMAT already exists but RUFF_OUTPUT_FILE has been missing.

A (simplified) GitLab CI job config for this scenario might look like this:

pre-commit:
  stage: test
  image: python
  variables:
    RUFF_OUTPUT_FILE: gl-code-quality-report.json
    RUFF_OUTPUT_FORMAT: gitlab
  before_script:
    - pip install pre-commit
  script:
    - pre-commit run --all-files --show-diff-on-failure
  artifacts:
    reports:
      codequality: gl-code-quality-report.json

Test Plan

I tested it manually.

[github-actions]

ruff-ecosystem results

Linter (stable)

✅ ecosystem check detected no linter changes.

Linter (preview)

✅ ecosystem check detected no linter changes.

[charliermarsh]

This seems reasonable to me.