fix(ir): 修改了一下context的管理

src/irgen/IRGenDecl.cpp

@@ -39,14 +39,14 @@ void IRGenImpl::GenVarDecl(SysYParser::VarDeclContext& decl) {
   if (storage_map_.find(&decl) != storage_map_.end()) {
     throw std::runtime_error("[irgen] 声明重复生成存储槽位");
   }
-  auto* slot = builder_.CreateAllocaI32(ir::DefaultContext().NextTemp());
+  auto* slot = builder_.CreateAllocaI32(module_.context().NextTemp());
   storage_map_[&decl] = slot;
 
   ir::Value* init = nullptr;
   if (decl.exp()) {
     init = GenExpr(*decl.exp());
   } else {
-    init = ir::DefaultContext().GetConstInt(0);
+    init = builder_.CreateConstInt(0);
   }
   builder_.CreateStore(init, slot);
 }