$ bjam --debug-configuration
This is useful if you think you are loading up a site-config.jam or a user-config.jam that you shouldn’t be. I was getting the following error after an upgrade to Intrepid Ibex:
error: at /usr/share/boost-build/build/project.jam:825 error: duplicate initialization of gcc with the following parameters: error: version = 4.3.2
Then I was able to find that the site-config.jam file in /etc/ was initializing gcc.