title: How to point LLVM_CONFIG environment variable to the path for llvm-config
body: <p>I am trying to install <code>numba</code> on an OS X Mountain Lion. I had tried the <code>pip install</code> way but didn't work, so I have downloaded from the GIT respositories the zip files. When trying to install numba I realized that I need <code>LLVM</code> first. </p>
  
  <p>I downloaded and unpacked <code>llvm</code> into the <code>Download</code> folder. The README instructions are: "If your LLVM is installed in a non-standard location, first point the <code>LLVM_CONFIG</code> environment variable to the path of the corresponding <code>llvm-config</code> executable."; a message compatible with the RunTimeError I get when running the <code>python setup.py install</code> command.</p>
  
  <p>My problem is that I don't understand what to do in order to make the <code>LLVM_CONFIG</code> environment variable to point to the corresponding <code>llvm-config</code> executable.</p>
  
  <p>Any help? Thanks</p>