title: pkg-config and OSX 10.8, proper PKG_CONFIG_PATH? Missing .pc files?
body: <p>I installed pkg-config with homebrew in OSX.  I'm not sure what I should set my PKG_CONFIG_PATH to?  Should it be a combination of /usr/include and /usr/local/include?  Even if I use one or the other, I get an error about there not being any .pc files, which I take it would contain info used by pkg-config?  Not sure what I'm doing wrong.  Help appreciated.</p>
  
  <pre><code>$ pkg-config --libs libxml2  
  Package libxml2 was not found in the pkg-config search path.  
  Perhaps you should add the directory containing `libxml2.pc'  
  to the PKG_CONFIG_PATH environment variable  
  No package 'libxml2' found
  </code></pre>
  
  <p>Update:
  So maybe I'm asking two different questions.  I just curled gsl and ran through the ./configure &amp;&amp; make &amp;&amp; sudo make install.  And with an empty $PKG_CONFIG_PATH I actually got a hit with:</p>
  
  <pre><code>pkg-config --libs gsl  
  -L/usr/local/lib -lgsl -lgslcblas -lm
  </code></pre>
  
  <p>But listing /usr/local/lib shows the gsl libs but no .pc files.  How come pkg-config works for custom installed packages in OSX but not default installed ones???</p>