title: How to use the ARG instruction of Dockerfile for Windows image
body: <p>I would like to pass an argument in my dockerfile to build my docker image. I've seen in other post and docker manual how to do this but it doesn't work in my case. 
  Here is an extract of my code where i use my argument: </p>
  
  <pre><code>ARG FirefoxVersion
  RUN powershell -Command iex ((new-object net.webclient).DownloadString('https://chocolatey.org/install.ps1'));
  RUN choco install -y firefox --version $FirefoxVersion --ignore-checksums
  </code></pre>
  
  <p>I build my image with this command in powershellPrompt : </p>
  
  <pre><code>docker build -t myimage --build-arg FirefoxVersion=61.0.1 .
  </code></pre>
  
  <p>Finally I have this error : </p>
  
  <pre><code> '$FirefoxVersion' is not a valid version string.
   Parameter name: version
   The command 'cmd /S /C choco install -y firefox --version $FirefoxVersion  -- ignore-checksums' returned a non-zero code: 1
  </code></pre>
  
  <p>Is someone know what is wrong with my code? 
  Thanks.</p>