Vue3.x的版本中build后dist文件中出现legacy的js文件问题

Usage: vue-cli-service build [options] [entry|pattern]

  Options:

    --mode         specify env mode (default: production)
    --dest         specify output directory (default: dist)
    --no-module    build app without generating <script type="module"> chunks for modern browsers
    --target       app | lib | wc | wc-async (default: app)
    --inline-vue   include the Vue module in the final bundle of library or web component target
    --formats      list of output formats for library builds (default: commonjs,umd,umd-min)
    --name         name for lib or web-component mode (default: "name" in package.json or entry filename)
    --filename     file name for output, only usable for 'lib' target (default: value of --name)
    --no-clean     do not remove the dist directory contents before building the project  
    --report       generate report.html to help analyze bundle content
    --report-json  generate report.json to help analyze bundle content
    --skip-plugins comma-separated list of plugin names to skip for this run
    --watch        watch for changes
    --stdin        close when stdin ends

> 1%
last 2 versions
not dead
not IE 11

"dependencies" : {},
"devDependencies": {},
"browserslist": [
  "> 1%",
  "last 2 versions",
  "not dead",
  "not ie 11"
]