Well spotted, but the correct approach is actually to use "sudo -E" instead of just "sudo" to inherit the current environment.
Otherwise you'd have to source the environment script within the new shell; sudo bash -c "source $path_to_gnustepsh && make install", perhaps?
And, are .profile and .bashrc even used in sudo's subshell out of the box?
sent from phone
Maybe you can add some «source GNUstep.sh» to your bashrc?