[CodeGen][NFCI] Avoid calls to setTargetAttributes on definitions

[alexgatea]

Summary

Avoid duplicate calls to setTargetAttributes on global variable definitions.

[cebowleratibm]

Suggest adding tag [NFCI] (no functional change intended)

[cebowleratibm]

I think it's appropriate to use the tag [Clang][NFCI] or [CodeGen][NFCI]

lib/CodeGen/CodeGenModule.cpp

if (Context.getLangOpts().CPlusPlus && GV->hasExternalLinkage() &&
             }
             emitter.finalize(GV);
           }
         }
       }
     }
   }
 
-  if (GV->isDeclaration()) {
+  if (D &&
+      D->isThisDeclarationADefinition(Context) == VarDecl::DeclarationOnly) {
     getTargetCodeGenInfo().setTargetAttributes(D, GV, *this);
     // External HIP managed variables needed to be recorded for transformation
     // in both device and host compilations.
     if (getLangOpts().CUDA && D && D->hasAttr<HIPManagedAttr>() &&
         D->hasExternalStorage())
       getCUDARuntime().handleVarRegistration(D, *GV);
   }