title: How pkg-config decides which look up path to add by default?
body: <p>I'm trying to run <code>pkg-config</code> on my 64bits elementary (ubuntu 14.04) from a .net gui application and it says that it doesn't find my packages that are found when I run the exact command from a terminal.</p>
  
  <p>For reference, here's the command: </p>
  
  <pre><code>pkg-config --cflags --libs  glib-2.0 gobject-2.0
  </code></pre>
  
  <p>Using the <code>PKG_CONFIG_DEBUG_SPEW</code> I managed to get detailed debug info for pkg-config and it looks like it initializes itself differently in the two cases.</p>
  
  <p>Initialization in .net gui application:</p>
  
  <pre><code>Adding directory '/usr/share/pkgconfig' from PKG_CONFIG_PATH
  Adding directory '/usr/lib/pkgconfig' from PKG_CONFIG_PATH
  </code></pre>
  
  <p>Initialization in terminal:</p>
  
  <pre><code>Adding directory '/usr/local/lib/x86_64-linux-gnu/pkgconfig' from PKG_CONFIG_PATH
  Adding directory '/usr/local/lib/pkgconfig' from PKG_CONFIG_PATH
  Adding directory '/usr/local/share/pkgconfig' from PKG_CONFIG_PATH
  Adding directory '/usr/lib/x86_64-linux-gnu/pkgconfig' from PKG_CONFIG_PATH
  Adding directory '/usr/lib/pkgconfig' from PKG_CONFIG_PATH
  Adding directory '/usr/share/pkgconfig' from PKG_CONFIG_PATH
  </code></pre>
  
  <p>Of course my libraries are defined in the missing directory '/usr/lib/x86_64-linux-gnu/pkgconfig' that is not added in the .net gui application.</p>
  
  <p><strong>Why are the two initializations different?</strong> </p>
  
  <p><strong>How can I tell pkg-config to initialize the same it does in the terminal?</strong></p>
  
  <blockquote>
    <p>Note: I know that I can set the <code>PKG_CONFIG_PATH</code> before calling pkg-config but I would prefer a simpler solution if available.</p>
  </blockquote>