title: podspec source :http unpacks to where?
body: <p>A podspec I'm creating is downloading a zip archive through a :http source:</p>
  
  <pre><code>s.source = {
    :http =&gt; 'https://developer.spotify.com/download/libspotify/libspotify-12.1.45-Darwin-universal.zip'
    }
  </code></pre>
  
  <p>I'm referring to files within the zip archive like so:</p>
  
  <pre><code>s.source_files = [
      'libspotify-12.1.45-Darwin-universal/libspotify.framework/Versions/12.1.45/Headers/*.h'
      ]
  s.preserve_paths = 'libspotify-12.1.45-Darwin-universal/libspotify.framework/*'
  s.xcconfig = {
    'FRAMEWORK_SEARCH_PATHS' =&gt; '\"$(PODS_ROOT)/libspotify-12.1.45-Darwin-universal\"'
    }
  </code></pre>
  
  <p>Passes pod spec lint validation, and pod install works well too in a project where I try out my podspec. But when building I get the error:</p>
  
  <blockquote>
    <p>ld: warning: directory not found for option
    '-F"/Users/niklas/code/playground/libspotify podspec
    test/Pods/libspotify-12.1.45-Darwin-universal"' ld: framework not
    found libspotify</p>
  </blockquote>
  
  <p>Getting this error because FRAMEWORK_SEARCH_PATHS is incorrectly set. There's no folder for the downloaded zip archive in the PODS_ROOT directory.</p>
  
  <p>Where should I point FRAMEWORK_SEARCH_PATHS to? Where's the extracted zip archive?</p>