How can I deploy GitLab pages in a subdirectory?

I have a repo like this:

• App // app source code
• Website // website source code, where my GitLab pages are

What I'd like is when i run .gitlab-ci.yml, it deploys all the files in the Website directory. Right now, I get errors when it tries to deploy. How can I achieve this? This is my current .gitlab-ci.yml:

image: ruby:2.3

variables:
  JEKYLL_ENV: production

before_script:
  - bundle install

test:
  stage: test
  script:
    - bundle exec jekyll build -d test
  artifacts:
    paths:
      - test
  except:
    - master

pages:
  stage: deploy
  script:
    - bundle exec jekyll build -d public
  artifacts:
    paths:
      - public
  only:
    - master