title: Dockerfile can't find output on linux
body: <p>I have the following Dockerfile</p>
  <pre><code>ARG JEKYLL_VERSION=4
  FROM jekyll/jekyll:$JEKYLL_VERSION as BUILD
  
  COPY --chown=jekyll:jekyll . /srv/jekyll
  RUN ls -lah /srv/jekyll
  
  RUN jekyll build
  RUN ls /srv/jekyll/_site/
  
  FROM nginxinc/nginx-unprivileged:alpine
  ADD build/nginx-site.conf /etc/nginx/conf.d/default.conf
  
  COPY --chown=101:101 --from=BUILD /srv/jekyll/_site/ /var/www
  </code></pre>
  <p>Which does build perfectly locally, but not on the Linux Jenkins Buildslave:</p>
  <pre><code>Bundle complete! 1 Gemfile dependency, 28 gems now installed.
  Use `bundle info [gemname]` to see where a bundled gem is installed.
  ruby 2.7.1p83 (2020-03-31 revision a0c7c23c9c) [x86_64-linux-musl]
  Configuration file: /srv/jekyll/_config.yml
              Source: /srv/jekyll
         Destination: /srv/jekyll/_site
   Incremental build: disabled. Enable with --incremental
        Generating... 
                      done in 0.186 seconds.
   Auto-regeneration: disabled. Use --watch to enable.
  Removing intermediate container 2b064db0ccaa
   ---&gt; 1e19e78f593a
  Step 6/9 : RUN ls /srv/jekyll/_site/
   ---&gt; Running in 194d35c3f691
  [91mls: /srv/jekyll/_site/: No such file or directory
  [0mThe command '/bin/sh -c ls /srv/jekyll/_site/' returned a non-zero code: 1
  </code></pre>
  <p>Changing <code>RUN jekyll build</code> to <code>RUN jekyll build &amp;&amp; ls /srv/jekyll/_site/</code> lists the jekyll output as expected.
  Why is the output of the <code>jekyll build</code> not stored? If I remove the <code>ls</code> command, the output can't be found in the later stage.
  Any hints?</p>