[flang] Fix warnings

This patch fixes:

  flang/../mlir/include/mlir/IR/TypeRange.h:51:19: error: 'ArrayRef'
  is deprecated: Use {} or ArrayRef<T>() instead
  [-Werror,-Wdeprecated-declarations]

  flang/../mlir/include/mlir/IR/ValueRange.h:401:20: error: 'ArrayRef'
  is deprecated: Use {} or ArrayRef<T>() instead
  [-Werror,-Wdeprecated-declarations]

Author: kazutakahirata

flang/include/flang/Optimizer/Builder/IntrinsicCall.h

@@ -753,7 +753,7 @@ static inline mlir::FunctionType genFuncType(mlir::MLIRContext *context,
   }
 
   if (TyR::ty == ParamTypeId::Void)
-    return mlir::FunctionType::get(context, argTypes, std::nullopt);
+    return mlir::FunctionType::get(context, argTypes, {});
 
   auto resType = getTypeHelper(context, builder, TyR::ty, TyR::kind);
   return mlir::FunctionType::get(context, argTypes, {resType});

flang/lib/Optimizer/Builder/IntrinsicCall.cpp

@@ -5150,9 +5150,9 @@ void IntrinsicLibrary::genIeeeGetOrSetModesOrStatus(
         isModes ? fir::runtime::genGetModesTypeSize(builder, loc)
                 : fir::runtime::genGetStatusTypeSize(builder, loc);
     byteSize = builder.createConvert(loc, builder.getIndexType(), byteSize);
-    addr =
-        builder.create<fir::AllocMemOp>(loc, extractSequenceType(heapTy),
-                                        /*typeparams=*/std::nullopt, byteSize);
+    addr = builder.create<fir::AllocMemOp>(loc, extractSequenceType(heapTy),
+                                           /*typeparams=*/mlir::ValueRange(),
+                                           byteSize);
     mlir::Value shape = builder.create<fir::ShapeOp>(loc, byteSize);
     builder.create<fir::StoreOp>(
         loc, builder.create<fir::EmboxOp>(loc, fieldTy, addr, shape), fieldRef);

flang/lib/Optimizer/Builder/PPCIntrinsicCall.cpp

@@ -2888,8 +2888,7 @@ void PPCIntrinsicLibrary::genVecStore(llvm::ArrayRef<fir::ExtendedValue> args) {
     llvm_unreachable("invalid vector operation for generator");
   }
 
-  auto funcType{
-      mlir::FunctionType::get(context, {stTy, addr.getType()}, std::nullopt)};
+  auto funcType{mlir::FunctionType::get(context, {stTy, addr.getType()}, {})};
   mlir::func::FuncOp funcOp = builder.createFunction(loc, fname, funcType);
 
   llvm::SmallVector<mlir::Value, 4> biArgs;