title: Xcode can’t launch project for debugging
body: <p>I’m using Xcode 4.6.3 to build a library for OS X. My project includes a target called <code>LibraryTest</code>, which is a command-line app to test the functionality of the library. Both the library and the test app build fine, but when I try to run the app it quits immediately and the debug console shows:</p>
  
  <pre><code>error: failed to launch '/Users/bdesham/Library/Developer/Xcode/DerivedData/Wavelength_and_Spectrum_Library-byosniusyaoidgdcpzwzuzkitzgv/Build/Products/Debug/LibraryTest'
  -- error: Host::LaunchProcess (launch_info) =&gt; pid=0,
  path='/Applications/Xcode.app/Contents/SharedFrameworks/LLDB.framework/Versions/A/Resources/debugserver'
  err = error: ::posix_spawnp (
      pid =&gt; 98649,
      path = '/Applications/Xcode.app/Contents/SharedFrameworks/LLDB.framework/Versions/A/Resources/debugserver',
      file_actions = 0x10b09e268,
      attr = 0x10b09e2a0,
      argv = 0x7fe2701377e0,
      envp = 0x0 )
  err = Bad file descriptor (0x00000009) (0x00000009)
  error: failed to launch '/Users/bdesham/Library/Developer/Xcode/DerivedData/Wavelength_and_Spectrum_Library-byosniusyaoidgdcpzwzuzkitzgv/Build/Products/Debug/LibraryTest'
  -- error: Host::LaunchProcess (launch_info) =&gt; pid=0,
  path='/Applications/Xcode.app/Contents/SharedFrameworks/LLDB.framework/Versions/A/Resources/debugserver'
  err = error: ::posix_spawnp (
      pid =&gt; 98649,
      path = '/Applications/Xcode.app/Contents/SharedFrameworks/LLDB.framework/Versions/A/Resources/debugserver',
      file_actions = 0x10b09e268,
      attr = 0x10b09e2a0,
      argv = 0x7fe2701377e0,
      envp = 0x0 )
  err = Bad file descriptor (0x00000009) (0x00000009)
  </code></pre>
  
  <p>(Line breaks added for readability.) I have the Xcode 5 DP installed, so I tried removing Xcode 4 and reinstalling it from the Mac App Store, but no dice. Deleting <code>DerivedData</code> didn’t help either. Any ideas?</p>