title: cannot execute RUN mkdir in a Dockerfile with space in directory name
body: <p>I want to create a file in C drive while building docker image and using command as below  </p>
  
  <pre><code>RUN mkdir "C:\Program Files\Microsoft Passport RPS"
  </code></pre>
  
  <p>but it throws error: </p>
  
  <pre><code>Step 6/6 : RUN mkdir "C:\Program Files\Microsoft Passport RPS"
   ---&gt; Running in ab58c6f2948d
  [91mmkdir : A positional parameter cannot be found that accepts argument 'Files\Microsoft'.
  At line:1 char:76
  + ... e = 'SilentlyContinue'; mkdir C:\Program Files\Microsoft Passport RPS
  [0m[91m+                             ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  [0m[91m    + CategoryInfo          : InvalidArgument: (:) [mkdir], ParentContainsErro 
  [0m[91m   rRecordException
  + FullyQualifiedErrorId : PositionalParameterNotFound,mkdir
  </code></pre>
  
  <p>Tried above command with forward as well as back slash.</p>
  
  <p>I have tried multiple other command as below:</p>
  
  <pre><code>ENV PATH_WITH_SPACE "C:/Program Files/Microsoft Passport RPS"
  RUN mkdir $[PATH_WITH_SPACE]
  
  RUN mkdir ["C:\Program Files\Microsoft Passport RPS"]
  </code></pre>
  
  <p>Can you please help me with appropriate command?</p>