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

[Shafik Yaghmour via cfe-commits]

================
@@ -4623,7 +4632,7 @@ void ASTWriter::GenerateSpecializationInfoLookupTable(
     Generator.insert(HashValue, Trait.getData(Specs, ExisitingSpecs), Trait);
   }
 
-  Generator.emit(LookupTable, Trait, Lookups ? &Lookups->Table : nullptr);
+  Generator.emit(LookupTable, Trait, nullptr);
----------------
shafik wrote:

```suggestion
  Generator.emit(LookupTable, Trait, /*Base=*/nullptr);
```
nit

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