[clang-tools-extra] [llvm] New check `misc-header-guard` (PR #177315)

[Baranov Victor via cfe-commits]

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+.. title:: clang-tidy - llvm-header-guard
+
+misc-header-guard
+=================
+
+Finds and fixes header guards.
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vbvictor wrote:

What do you mean by `fixes`? Can we elaborate here a bit how it fixes and what corrections are made.

https://github.com/llvm/llvm-project/pull/177315