The variable is not set anymore by the UseIt.sh script, so if a user doesn't
have it set in the .bashrc or .zshrc file already, it's not working properly.
Ports/.port_include.sh, Toolchain/BuildIt.sh, Toolchain/UseIt.sh
have been left largely untouched due to use of Bash-exclusive
functions and variables such as $BASH_SOURCE, pushd and popd.