title: Building a cmake project which uses boost with a local distribution
body: <p>I'm trying to build kenlm which uses boost. The version of boost already installed on the system seems incompatible or too old or broken.</p>
  <p>I have successfully built a copy of boost in my <code>~/local directory</code>. I would like to tell cmake to use the boost headers found under <code>~/local/include</code> and the libraries in <code>~/local/lib</code> instead. However I can't see how to tell cmake to look at my custom path for libraries or headers. I've tried setting <code>LD_LIBRARY_PATH</code> to <code>~/local/lib:$LD_LIBRARY_PATH</code>. Is there an equivalent variable for include path as well? I haven't been able to find one.</p>
  <p>If there is no way to do this with just environment flags, I've been trying to edit the <code>CMakeLists.txt</code> file but haven't had much success. I tried editing in my include path but it still uses whatever <code>find_package(Boost ..)</code> finds which is the <code>/usr/include</code> header.</p>