title: sencha command not found using docker
body: <p>I'm trying to build an image for sencha using ruby:alpine and following the instructions indicated in this <a href="https://docs.sencha.com/extjs/6.0.2/guides/getting_started/getting_started.html" rel="nofollow noreferrer">link</a></p>
  
  <p>As the title says, i can't get alpine to recognize sencha command. this <a href="https://docs.sencha.com/cmd/guides/intro_to_cmd.html#intro_to_cmd_-_command_not_found" rel="nofollow noreferrer">link</a> suggest that I should have sencha in the PATH environment variable (it also says that I should close the terminal and open a new one, but I don't know if that's even possible)</p>
  
  <p>I tried to add sencha to the PATH variable by writing this in my dockerfile</p>
  
  <pre><code>RUN export PATH = /my/path/to/sencha/cmd:$PATH
  </code></pre>
  
  <p>Note that in this case <code>$PATH</code> in not an <code>ENV</code> element. After that, I add <code>RUN echo $PATH</code> to check if the path was actually added to the variable, but it seems that it didn't work...</p>
  
  <p>Next step calls <code>RUN sencha</code>, where I get the error of command not found</p>