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

[Jinjie Huang via cfe-commits]

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@@ -462,6 +462,9 @@ OptionalFileEntryRef HeaderSearch::getFileAndSuggestModule(
     return std::nullopt;
   }
 
+  if (!NeedSuggest)
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Jinjie-Huang wrote:

Only suggest the module during the first lookup, consistent with the baseline

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