title: An issue with postinst-intercept scripts
body: <p>I trying to integrate Yocto 2.6.2 due to higher version packages requests from Software team. Except regular <code>oe bitbake</code>, in our company we have another build system which is based on python also. I am not familiar too much with it but it invokes bitbake too. Just it fetches the layers from company servers because it is not able to do it from the net and put some additional data. The issue is following. With regular bitbake everything is fine and the build goes smoothly. When I run our proprietary build system it fails on <code>do_rootfs</code> with the following reason copied from the log:</p>
  <pre><code>**NOTE: Running intercept scripts:**
  **NOTE: &gt; Executing update_icon_cache intercept ...**
  **NOTE: Exit code 127. Output:**
  **/home/w23698/projects/btstmp/builds/home/w23698/projects/proj_csc5_clean/proj_csc5/srcMirror/build/tmp/work/csc5-poky-linux-gnueabi/ww-image/1.0-r0/intercept_scripts-12c5ef04e386052464955905a231f7ec3a3eb8c0452bbf7c1cd0f436ca99cbf7/update_icon_cache: 6: /home/w23698/projects/btstmp/builds/home/w23698/projects/proj_csc5_clean/proj_csc5/srcMirror/build/tmp/work/csc5-poky-linux-gnueabi/ww-image/1.0-r0/intercept_scripts-12c5ef04e386052464955905a231f7ec3a3eb8c0452bbf7c1cd0f436ca99cbf7/update_icon_cache: /home/w23698/projects/btstmp/builds/home/w23698/projects/proj_csc5_clean/proj_csc5/srcMirror/build/tmp/work/csc5-poky-linux-gnueabi/ww-image/1.0-r0/recipe-sysroot-native//gdk-pixbuf-2.0/gdk-pixbuf-query-loaders: not found**
  
  **ERROR: The postinstall intercept hook 'update_icon_cache' failed, details in /home/w23698/projects/btstmp/builds/home/w23698/projects/proj_csc5_clean/proj_csc5/srcMirror/build/tmp/work/csc5-poky-linux-gnueabi/ww-image/1.0-r0/temp/log.do_rootfs**
  
  **DEBUG: Python function do_rootfs finished**
  **ERROR: Function failed: do_rootfs**
  </code></pre>
  <p>In the normal bitbake the invoked intercept (update_gio_module_cache intercept) script is very different and it passes.
  Where the decision which intercept script to call is made?</p>
  <p>I notified that all the intercept scripts in the proprietary build system are chmoded to x. I made one very simple try to match the access flags as per original yocto poky layer. It didn't help.</p>