[clang] [Clang][Sema] Change `ExtnameUndeclaredIdentifiers` to MapVector. (PR #193924)

[Alexander Kornienko via cfe-commits]

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@@ -5,6 +5,19 @@
 // RUN: %clang_cc1 -triple=x86_64-unknown-linux -x c-header -emit-pch -o %t %S/pragma-redefine-extname.h
 // RUN: %clang_cc1 -triple=x86_64-unknown-linux -include-pch %t %s -verify -emit-llvm -o - | FileCheck %s
 
+/// Compile it again to check that the pch file is deterministic.
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alexfh wrote:

I'd leave just one comment here: `// Compile it a few times to check that the PCH file is deterministic.` and remove the ones below.

https://github.com/llvm/llvm-project/pull/193924