[clang] [CIR] Defer declarations and tentative definitions (PR #141700)

[Henrich Lauko via cfe-commits]

================
@@ -135,6 +135,10 @@ class CIRGenConsumer : public clang::ASTConsumer {
     }
     }
   }
+
+  void CompleteTentativeDefinition(VarDecl *D) override {
+    Gen->CompleteTentativeDefinition(D);
+  }
----------------
xlauko wrote:

```suggestion
  void CompleteTentativeDefinition(VarDecl *d) override {
    Gen->CompleteTentativeDefinition(d);
  }
```

https://github.com/llvm/llvm-project/pull/141700