Add [[maybe_unused]] to EmplaceStatus for type map (#3132)

Signed-off-by: Sidorov, Dmitry <dmitry.sidorov@intel.com>

Original commit:
KhronosGroup/SPIRV-LLVM-Translator@8011eaf0c686ecc

Author: MrSidims

llvm-spirv/lib/SPIRV/SPIRVWriter.cpp

@@ -2697,7 +2697,7 @@ LLVMToSPIRVBase::transValueWithoutDecoration(Value *V, SPIRVBasicBlock *BB,
 
 SPIRVType *LLVMToSPIRVBase::mapType(Type *T, SPIRVType *BT) {
   assert(!T->isPointerTy() && "Pointer types cannot be stored in the type map");
-  auto EmplaceStatus = TypeMap.try_emplace(T, BT);
+  [[maybe_unused]] auto EmplaceStatus = TypeMap.try_emplace(T, BT);
   assert(EmplaceStatus.second && "The type was already added to the map");
   SPIRVDBG(dbgs() << "[mapType] " << *T << " => "; spvdbgs() << *BT << '\n');
   return BT;