title: ENV/ARG command not populating variables in Dockerfile
body: <p>I'm trying to create a nanoserver w/ nodejs base image, but I can't seem to get the ARG (or ENV) command to work properly.</p>
  
  <p>My docker file:</p>
  
  <pre><code>FROM microsoft/nanoserver
  
  ENV NODE_VERSION=8.11.4
  
  ADD https://nodejs.org/dist/v${NODE_VERSION}/node-v${NODE_VERSION}-win-x64.zip C:\\build\\node-v${NODE_VERSION}-win-x64.zip
  
  
  RUN powershell -Command Expand-Archive C:\build\node-v${NODE_VERSION}-win-x64.zip C:\; Rename-Item C:\node-v${NODE_VERSION}-win-x64 node
  RUN SETX PATH C:\node
  
  ENTRYPOINT C:\node\node.exe
  </code></pre>
  
  <p>Build command:</p>
  
  <pre><code>docker build . -t base-image:latest
  </code></pre>
  
  <p>It downloads the zip file, but when it tries to rename the downloaded file it throws an error: </p>
  
  <pre><code>Expand-Archive : The path 'C:\build\node-v-win-x64.zip' either does not exist
  or is not a valid file system path.
  </code></pre>