[llvm] [llvm-libgcc][CMake] Refactor llvm-libgcc (PR #65455)

[Fangrui Song via llvm-commits]

MaskRay wrote:

> @MaskRay It seems that Github enforce a column limit of 70 characters in "Squash and Merge" commit messages ([refined-github#1475](https://github.com/refined-github/refined-github/issues/1475)). Commit messages targeting a 80 character limitation will be truncated again when texts are copied and pasted directly with original line breakages ([7ac1f60](https://github.com/llvm/llvm-project/commit/7ac1f60f01a73f9678bba2385e933864ecce8622) and [af935cf](https://github.com/llvm/llvm-project/commit/af935cf0ee8a26dcf0860ed0c72d74b4a1cb1314)). Should we mention this behaviour in documents for the Github PR transition?

Thanks for mentioning this behavior. Perhaps comment on https://discourse.llvm.org/t/hows-it-going-with-pull-requests/73467 or a related github pr transition post?

Due to email spam from github notifications, I almost missed your comment...

https://github.com/llvm/llvm-project/pull/65455