[clang] [clang-tools-extra] [flang] [lldb] [llvm] [openmp] [pstl] Finally formalise our defacto line-ending policy (PR #86318)

[Aaron Ballman via cfe-commits]

AaronBallman wrote:

> @AaronBallman you said this has happened before, but I don't see this in history. Can you link to the commit to which you're referring?
> 
> I only see one other commit ([9783f28](https://github.com/llvm/llvm-project/commit/9783f28cbb155e4a8d49c12e1c60ce14dcfaf0c7)) that touches the root `.gitattributes`

https://reviews.llvm.org/D124563 and https://reviews.llvm.org/D124606 where there was a lot of back and forth on the changes after they landed, but I may have missed some discussions too.

https://github.com/llvm/llvm-project/pull/86318