feat: add a --clean-cache command to clean up locations specified at CIBW_CACHE_PATH (#2489)

* Add `clean_cache` to command-line arguments

* Add `--clean-cache` to parser

* Add logic

* Add test to clean cache when it exists

* Ad test to run cache cleaning when none exists

* Add test to run cache cleaning on unwritable path

* Use `main()` instead

* tests: move command tests

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>

* Create cibuildwheel cache sentinel file

* Add sentinel to existing tests + add new test

* Add signature and switch to `CACHEDIR.TAG`

Co-authored-by: Henry Schreiner <HenrySchreinerIII@gmail.com>

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* Another instance to replace with `CACHEDIR.TAG`

* Verify `CACHEDIR.TAG` signature

* Simplify code branching and control flow

* Add test

* Add link to `CACHEDIR.TAG` specification

* Write with UTF-8 encoding

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

---------

Signed-off-by: Henry Schreiner <henryschreineriii@gmail.com>
Co-authored-by: Henry Schreiner <henryschreineriii@gmail.com>
Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

cibuildwheel/options.py

@@ -63,6 +63,7 @@ class CommandLineArguments:
     allow_empty: bool
     debug_traceback: bool
     enable: list[str]
+    clean_cache: bool
 
     @classmethod
     def defaults(cls) -> Self:
@@ -77,6 +78,7 @@ class CommandLineArguments:
             print_build_identifiers=False,
             debug_traceback=False,
             enable=[],
+            clean_cache=False,
         )