title: Build fails with "Command failed with a nonzero exit code"
body: <p>When I try to build my app with Xcode, an error interrupts the build process:</p>
  
  <blockquote>
    <p>Command <code>CompileStoryboard</code> failed with a nonzero exit code</p>
  </blockquote>
  
  <p>Sometimes, it shows this error instead:</p>
  
  <blockquote>
    <p>Command <code>CompileSwift</code> failed with a nonzero exit code</p>
  </blockquote>
  
  <p>I have <strong>New Build System</strong> turned on.</p>
  
  <p>What can I do to fix this?</p>