[clang] Remove unused selStructPtrTy in CGObjCGNU.cpp (NFC)

/llvm-project/clang/lib/CodeGen/CGObjCGNU.cpp:3674:15: error: variable 'selStructPtrTy' set but not used [-Werror,-Wunused-but-set-variable]
  llvm::Type *selStructPtrTy = SelectorTy;
              ^
1 error generated.

Author: DamonFool

clang/lib/CodeGen/CGObjCGNU.cpp

@@ -3671,11 +3671,9 @@ llvm::Function *CGObjCGNU::ModuleInitFunction() {
   GenerateProtocolHolderCategory();
 
   llvm::StructType *selStructTy = dyn_cast<llvm::StructType>(SelectorElemTy);
-  llvm::Type *selStructPtrTy = SelectorTy;
   if (!selStructTy) {
     selStructTy = llvm::StructType::get(CGM.getLLVMContext(),
                                         { PtrToInt8Ty, PtrToInt8Ty });
-    selStructPtrTy = llvm::PointerType::getUnqual(selStructTy);
   }
 
   // Generate statics list: