title: Bridging header not found when creating app extension
body: <p>Trying to create a document provider app extension for my app, returns me this error when I try to run the project after creating the app extension (just creating it not adding anything else) :</p>
  
  <blockquote>
    <p>error: bridging header '/myPath/test-Bridging-Header.h' does not exist</p>
  </blockquote>
  
  <p>Apparently the app extension is not searching at the right path, the bridging header is in the folder with all the classes and the app extension is looking for it at the root of the project.
  Any fix?</p>