[llvm] [CodingStandard] Require Unix line endings for C/C++ source and headers (PR #161228)

[Rahul Joshi via llvm-commits]

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@@ -1790,6 +1790,13 @@ would help to avoid running into a "dangling else" situation.
       markAsIgnored(D);
   }
 
+Use Unix style line endings for source files
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jurahul wrote:

Right, I don't know/think if there is anything in github that flags this. Yeah, a liner for this would be nice. Looks like `file` reports this, so it may be a matter of plugging it in the github CI. But we also need to know which files in the repo are source files vs not, maybe that can be done at the directory level. 

Actually, does clang-tidy have such a check? 

https://github.com/llvm/llvm-project/pull/161228