[clang] [clang] Support header shadowing diagnostics in Clang header search (PR #162491)

[Qiu Chaofan via cfe-commits]

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@@ -414,6 +404,9 @@ Improvements to Clang's diagnostics
 - Clang now emits a diagnostic in case `vector_size` or `ext_vector_type`
   attributes are used with a negative size (#GH165463).
 
+- A new warning ``-Wshadow-header`` has been added to detect when a header file
+  is found in multiple search directories(excluding system paths).
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ecnelises wrote:

nit: space before left parenthesis

https://github.com/llvm/llvm-project/pull/162491