If you have macports libraries installed that shadow libraries in src/third_party, then the injection of -I/opt/local/include on the compile line means that the headers from macports will be used preferentially to the headers from third_party, but we will still link against the object files compiled in third_party. This is doomed to failure, and the build will fail in very non-obvious ways.

Similar difficulties may occur if you had the mongo client driver installed in /opt/local.

The additional include paths (and probably library paths) should follow our third_party and intrinsic includes. The same issue exists for the /sw/include and /sw/lib options.