[clang] [Serialization] [ASTWriter] Try to not record namespace as much as possible (PR #179178)

[Shafik Yaghmour via cfe-commits]

================
@@ -4856,9 +4860,7 @@ void ASTWriter::GenerateNameLookupTable(
       TULookupGenerator.insert(Key, TULocalTrait.getData(IDs), TULocalTrait);
     }
 
-    auto *TULocalLookups = Chain ? Chain->getTULocalLookupTables(DC) : nullptr;
-    TULookupGenerator.emit(TULookupTable, TULocalTrait,
-                           TULocalLookups ? &TULocalLookups->Table : nullptr);
+    TULookupGenerator.emit(TULookupTable, TULocalTrait, nullptr);
----------------
shafik wrote:

```suggestion
    TULookupGenerator.emit(TULookupTable, TULocalTrait, /*Base=*/nullptr);
```

https://github.com/llvm/llvm-project/pull/179178