[clang] [lldb] [clang][AST] fix ast-print of extern <lang> with >=2 declarators, fixed (PR #93913)

[Aaron Ballman via cfe-commits]

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@@ -2380,7 +2380,7 @@ FunctionDecl *Sema::CreateBuiltin(IdentifierInfo *II, QualType Type,
   }
 
   FunctionDecl *New = FunctionDecl::Create(Context, Parent, Loc, Loc, II, Type,
-                                           /*TInfo=*/nullptr, SC_Extern,
+                                           /*TInfo=*/nullptr, SC_None,
----------------
AaronBallman wrote:

> You are right, I also paid attention to that issue. However, when a storage class specifier is omitted for a function, it's storage class is implicitly supposed to be extern. Thus, it's fine.

That's not actually correct -- the declaration of a function at block scope should definitely *not* be extern, it should have no linkage: https://godbolt.org/z/81fMaPaTq

> Furthermore, the meaning of this field according to the documentation comments is not for the actual storage duration or linkage, but for the storage-class specifier as present in the source code. Since builtins aren't really present in the source code, it seems further reasonable to omit a specifier.

Builtins should behave as-if they were declared in a header file that was included in the TU, and so they typically would be marked as `extern`.

https://github.com/llvm/llvm-project/pull/93913