R2 does not detect correct external programs.

Even though the external programs are not mandatory, but for some of the usage I would need to use those programs, but for some reason, R2 does not correctly detect any of the installed external programs, such as gzip, unrar, etc etc, they are installed, because when I run each of the commands with the --help option, in a console, I get the displayed help for each of the commands.

What line(s) in the install files would I need to change for R2 to detect those programs?