title: Clang: Output a 32 AND 64 bit combination .dylib
body: <p>I've seen dylibs that are both 32 and 64 bit when performed the <code>file</code> command on. How do I go about building one in Clang? </p>
  
  <p>The -m32 flag creates 32 bit dylib, -m64 makes 64 bit, but using both of them doesn't work.</p>
  
  <p>Edit: For instance, here's the output of <code>file</code> on the type of dylib I'm trying to build</p>
  
  <pre><code>file /Library/Frameworks/SDL.framework/Versions/A/SDL 
  /Library/Frameworks/SDL.framework/Versions/A/SDL: Mach-O universal binary with 2 architectures
  /Library/Frameworks/SDL.framework/Versions/A/SDL (for architecture x86_64): Mach-O 64-bit dynamically linked shared library x86_64
  /Library/Frameworks/SDL.framework/Versions/A/SDL (for architecture i386):   Mach-O dynamically linked shared library i386
  </code></pre>