fix: force windows compiler to run in out_dir to prevent artifacts in cwd

[wmmc88]

MSVC was dumping flag_check.exe in the crate's root directory whenever is_flag_supported_inner was called. This PR changes the cwd of the compiler to be in out_dir, adds a local github action to check whether the git working tree is clean, and then uses that action to check that the CI pipelines that produce artifacts haven't dumped anything in the git working tree.

GitHub Actions and Workflow Improvements:

• .github/actions/check-clean-git-working-tree/action.yaml: Added a new action named "Check Clean Git Working Tree" to verify that the Git working tree is clean.
• .github/workflows/main.yml: Integrated the new "Check Clean Git Working Tree" action into various job steps to prevent bugs related to uncommitted changes. [1] [2] [3] [4] [5] [6]
• .github/workflows/main.yml: Updated several job steps to use the ${{ runner.temp }} directory for temporary files. [1] [2]

Codebase Simplification:

• src/lib.rs: Simplified the Build implementation by directly calling methods on the compiler object instead of storing their results in temporary variables. [1] [2] [3]
• src/lib.rs: Ensured the cmd command runs in the out_dir directory by using the current_dir method.

fixes #1411

[NobodyXu]

Thank you, LGTM