[clang] [clang] fix definition data not being propagated to all redecls (PR #157019)

[Chuanqi Xu via cfe-commits]

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@@ -2107,6 +2107,8 @@ void ASTDeclMerger::MergeDefinitionData(
     auto *Def = DD.Definition;
     DD = std::move(MergeDD);
     DD.Definition = Def;
+    for (auto *TD : Def->redecls())
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ChuanqiXu9 wrote:

I am not sure if we should use `noload_redecls()` since redecls may trigger loading.

https://github.com/llvm/llvm-project/pull/157019