[clang] [clang-tools-extra] [clang-tidy] Avoid processing declarations in system headers (PR #128150)

[Gábor Horváth via cfe-commits]

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@@ -91,6 +91,10 @@ Improvements to clang-query
 Improvements to clang-tidy
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+- It no longer processes declarations from system headers by default, greatly
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Xazax-hun wrote:

I think we should mention somewhere that downstream users might need to modify their own checks as this might change their behavior by default. 

https://github.com/llvm/llvm-project/pull/128150