title: #import "directory/file.h" not found from a cross directory
body: <p>I am trying to import a header from a file across sibling directories.</p>
  
  <p>The project looks like this:</p>
  
  <pre>
  Project.xcodeproj
    SubdirA
      FileA.h
      FileA.m
    SubdirB
      FileB.h
      FileB.m
  </pre>
  
  <p>In <code>SubdirA/FileA.m</code>:</p>
  
  <pre><code>#import "FileA.h"
  #import "SubdirB/FileB.h"
  </code></pre>
  
  <p>I can only get this to work if I change the second #import to:</p>
  
  <pre><code>#import "../SubdirB/FileB.h"
  </code></pre>
  
  <p>I have the parent directory of SubdirA and SubdirB in <code>USER_HEADER_SEARCH_PATHS</code> as <code>$(PROJECT_DIR)</code>. My understanding is that the #import "SubdirB/FileB.h" should be attempted from both FileA's directory and each of the paths in <code>USER_SEARCH_PATHS</code>. So this should work.</p>
  
  <p>What's the proper way of fixing this? I've hit this in the past, but can never remember how to fix it.</p>