title: autogen.sh: You need gtk-doc to build this package
body: <p>I want to compile <a href="https://github.com/lxde/libfm" rel="noreferrer">LXDE's libfm</a> from source, but when I run <code>./autogen.sh</code>, it fails with this error:</p>
  
  <pre><code>You need gtk-doc to build this package.
  </code></pre>