vite: Unable to support functions such as "optional chain" in QQ browser 10 or chrome 70

Describe the bug

Invalid Babel configuration

// App.vue

const num = window?.num ?? 9;
console.log(num);

// babel.config.js

module.exports = {
  presets: [
    "@vue/cli-plugin-babel/preset",
    "@babel/plugin-proposal-optional-chaining"
  ]
};

// vite.config.ts

import { defineConfig } from 'vite'
import vue from '@vitejs/plugin-vue'
import legacy from '@vitejs/plugin-legacy'
import babel from 'vite-babel-plugin'

// https://vitejs.dev/config/
export default defineConfig({
  plugins: [
    vue(),
    (babel as any)(),
    // legacy({
    //   additionalLegacyPolyfills: ['@babel/plugin-proposal-optional-chaining'],
    //   targets: ['chrome 70']
    // })
  ],
  build: {
    target: ['es2015'],
    // target: ['chrome70']
  },
})

Reproduction

https://github.com/yangdan8/vite2-vue3-ts-demo

System Info

QQ browser 10
Chrome70

Used Package Manager

yarn

Logs

Uncaught SyntaxError: Unexpected token .

Validations

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• Read the Contributing Guidelines.
• Read the docs.
• Check that there isn’t already an issue that reports the same bug to avoid creating a duplicate.
• Make sure this is a Vite issue and not a framework-specific issue. For example, if it’s a Vue SFC related bug, it should likely be reported to https://github.com/vuejs/vue-next instead.
• Check that this is a concrete bug. For Q&A open a GitHub Discussion or join our Discord Chat Server.
• The provided reproduction is a minimal reproducible example of the bug.