title: Can't add linker flag to cocoa pods spec
body: <p>I need to include in my cocoa pods spec option to pass the <code>-lz</code> flag in <code>Other linker flags</code> section.</p>
  
  <p>For this I tried to use:</p>
  
  <pre><code>"compiler_flags" : "-lz"
  </code></pre>
  
  <p>or </p>
  
  <pre><code>"compiler_flags" : [
      "-lz"
  ]
  </code></pre>
  
  <p>but flag doesn't appear in build settings.</p>
  
  <p>What am I doing wrong?</p>