为什么在构建然后部署时必须运行两次构建？

Question

这是一个共同的主题吗？例如：构建时我已经在构建。但是当我部署Web应用程序时，我又将其构建了两次吗？这是正确的方法吗？如果是这样，为什么会这样呢？

build site:
  image: node:latest
  stage: build
  script:
    - npm install --progress=false
    - npm run build
  artifacts:
    expire_in: 1 week
    paths:
      - dist

pages: 
  image: node:latest
  stage: deploy
  script:
    - npm install --progress=false
    - npm run build
    - rm -rf public
    - mkdir public
    - cp -r dist/* public
  artifacts:
    expire_in: 1 week
    paths:
      - public # artifact path must be /public for GitLab Pages to pick it up
  only:
    - master