build: wrong keep classnames options (#9750)

tools/cli/src/webpack/index.ts

@@ -42,9 +42,10 @@ const OptimizeOptionOptions: (
         compress: {
           unused: true,
         },
-        mangle: true,
+        mangle: {
           keep_classnames: true,
         },
+      },
     }),
   ],
   removeEmptyChunks: true,