title: Passing sudo flags into makefile
body: <p>I am currently located behind a proxy.  Sitting in the land of bash, I have my HTTP_PROXY and HTTPS_PROXY set as environment variables set to the proxy.  When I want to install something under sudo, like pip, I have to use the -E flag with sudo to get the install to work:</p>
  
  <pre><code>sudo -E pip install 'selenium&gt;=2.40.0'
  </code></pre>
  
  <p>That is fine and works.</p>
  
  <p>However I have some across a Makefile that calls sudo pip install.  Even if I call make with the -E flag</p>
  
  <pre><code>sudo -E make install
  </code></pre>
  
  <p>The -E flag from sudo is no picked up in the Makefile when the makefile tries to do an installation from pip (that I am using)</p>
  
  <p>Is is possible for a Makefile to pick up the flags used when calling the sudo command?</p>