title: vue-cli not transpiling code to es5 or commonjs when using the target wc build option
body: <p>I'm trying to build a component using:</p>
  
  <p><code>vue-cli-service build --target wc --name my-component ./src/App.vue</code></p>
  
  <p>The outputted build js still has <code>const</code> and arrow functions. How can I have it transpile to commonjs for example?</p>
  
  <p>I've tried using various presets in the babel config but the build result is still the same.</p>
  
  <p>There is a <code>babel.config.js</code> file in project root (generated from vue-cli)</p>
  
  <pre><code>module.exports = {
    presets: [
    '@vue/app'
    ]
  }
  
  </code></pre>
  
  <p>No errors, the build is occurring but it is not transpiling. It's almost as if the babel config is bypassed when building with target wc</p>