Enable CI on Windows hosts for autotools

[arixmkii]

Pull request checklist

Please check if your PR fulfills the following requirements:

• [X] Tests for the changes have been added (for bug fixes / features)
• [X] Docs have been reviewed and added / updated if needed (for bug fixes / features)
• [X] Build was run locally and without warnings or errors
• [X] All previous and new tests pass

Pull request type

Please check the type of change your PR introduces: - [ ] Bugfix - [ ] Feature - [ ] Code style update (formatting, renaming, typo fix) - [ ] Refactoring (no functional changes, no api changes) - [X] Build related changes - [ ] Documentation content changes - [ ] Other (please describe): ## What is the current behavior?

No Windows CI at all.

Related Issue URL: https://github.com/tukaani-project/xz/issues/18

What is the new behavior?

• autotools build set for Windows added
• build is using msys2 with UCRT64 toolchain

Does this introduce a breaking change?

• [ ] Yes
• [X] No

Other information

CMake build part is not provided as part of this PR.

Additional changes:

• bumped checkout action to v3 (not really critical, but I did while trying to understand build failure)
• fixed "false positive" uninitialized warning with empty in stream_encoder.c
• fixed missing include in memcmplen.h, because this include is not provided if --disable-threads is requested for build

Windows build run is very slow (comparing to others), but I don't think it could be somehow improved.

[arixmkii]

This is how it looked in my fork.

[arixmkii]

Thank you for detailed feedback! 👍 Will rework the changes and group them into logically separated commits.