yarn build generator two same css files

[Senasiko]

Version

5.0.0-beta.1

Reproduction link

https://github.com/Senasiko/vue-cli-reproduction

Environment info

Environment Info:

  System:
    OS: macOS 11.2.3
    CPU: (8) x64 Intel(R) Core(TM) i7-7700HQ CPU @ 2.80GHz
  Binaries:
    Node: 14.15.0 - /usr/local/bin/node
    Yarn: 1.22.10 - /usr/local/bin/yarn
    npm: 6.14.8 - /usr/local/bin/npm
  Browsers:
    Chrome: 90.0.4430.212
    Edge: Not Found
    Firefox: 87.0
    Safari: 14.0.3
  npmPackages:
    @vue/babel-helper-vue-jsx-merge-props:  1.2.1
    @vue/babel-helper-vue-transform-on:  1.0.2
    @vue/babel-plugin-jsx:  1.0.6
    @vue/babel-plugin-transform-vue-jsx:  1.2.1
    @vue/babel-preset-app:  5.0.0-beta.1
    @vue/babel-preset-jsx:  1.2.4
    @vue/babel-sugar-composition-api-inject-h:  1.2.1
    @vue/babel-sugar-composition-api-render-instance:  1.2.4
    @vue/babel-sugar-functional-vue:  1.2.2
    @vue/babel-sugar-inject-h:  1.2.2
    @vue/babel-sugar-v-model:  1.2.3
    @vue/babel-sugar-v-on:  1.2.3
    @vue/cli-overlay:  5.0.0-beta.1
    @vue/cli-plugin-babel: ~5.0.0-beta.1 => 5.0.0-beta.1
    @vue/cli-plugin-eslint: ~5.0.0-beta.1 => 5.0.0-beta.1
    @vue/cli-plugin-router:  5.0.0-beta.1
    @vue/cli-plugin-vuex:  5.0.0-beta.1
    @vue/cli-service: ~5.0.0-beta.1 => 5.0.0-beta.1
    @vue/cli-shared-utils:  5.0.0-beta.1
    @vue/compiler-core:  3.0.11
    @vue/compiler-dom:  3.0.11
    @vue/compiler-sfc: ^3.0.4 => 3.0.11
    @vue/compiler-ssr:  3.0.11
    @vue/component-compiler-utils:  3.2.0
    @vue/reactivity:  3.0.11
    @vue/runtime-core:  3.0.11
    @vue/runtime-dom:  3.0.11
    @vue/shared:  3.0.11
    @vue/web-component-wrapper:  1.3.0
    eslint-plugin-vue: ^7.2.0 => 7.9.0
    vue: ^3.0.4 => 3.0.11
    vue-eslint-parser:  7.6.0
    vue-hot-reload-api:  2.3.4
    vue-loader:  16.2.0 (15.9.7)
    vue-style-loader:  4.1.3
    vue-template-es2015-compiler:  1.9.1
  npmGlobalPackages:
    @vue/cli: Not Found

Steps to reproduce

yarn build
look at ./dist/css, has two same css files.

What is expected?

just one css file

What is actually happening?

two css files