title: Swift command line tool runtime crash dyld: Symbol not found: __pthread_atfork_child
body: <p>When I build any swift command line tool it always crashes (<code>Thread 1: signal SIGABRT</code>) right after launch with:</p>
  
  <pre><code>dyld: Symbol not found: __pthread_atfork_child
    Referenced from: /usr/lib/libSystem.B.dylib
    Expected in: /usr/lib/libSystem.B.dylib
   in /usr/lib/libSystem.B.dylib
  Program ended with exit code: 9
  </code></pre>
  
  <p>This happens to any command line tool I build. Even when I build the xcode command line tool template.</p>
  
  <p>Reseting the mac to an earlier time machine backup fixed the issue for a day. Then it came back for no reason.
  However I am able to build command line tools using the swift cli and package manager.</p>
  
  <p>I'm using Xcode 8 on macOS 10.12.5</p>