If I look at your mozconfig file I do not see the following 2 option:
# Point to the Xulrunner libraries - comment these for a standalone browser.
The installation notes for Firefox say the following about these 2 options:
If you are not building against Xulrunner you must comment the 'Xulrunner' items.
It seems that you are using Xulrunner and thus these 2 should be present and not commented out.
Hope this helps.