The poorly documented ~/.pydistutils.cfg allows setting defaults for command-line arguments to distutils setup.py commands such as python setup.py build_ext --library-dirs. Use this to get easy_install to build eggs with extension modules that need to find libaries on multi-arch systems like Ubuntu and Debian. Just add the following two lines to ~/.pydistutils.cfg:
[build_ext] library_dirs = /usr/lib:/usr/lib/i386-linux-gnu:/usr/local/lib