title: Xcode: add files to project in a build phase
body: <p>In my Xcode project I have a custom build phase which runs a script and downloads some images for use by the app. What I want to do is to automatically add those image to the project during the build. Right now, I have to build once (which downloads the files), and then manually add those files to the project. It works as long as the file names don't change. Instead, I'd like to add all the files in a specific directory to the project.</p>
  
  <p>I've tried setting the Output Files value, as suggested <a href="https://stackoverflow.com/questions/1371351/add-files-to-an-xcode-project-from-a-script">here</a>, like this: </p>
  
  <pre><code>$(PROJECT_DIR)/$(PROJECT_NAME)/External Assets/*
  </code></pre>
  
  <p>but it doesn't work. Any idea if this can be done?</p>