I was able to fix this by manually editing Makefile.in and correcting all the paths to the executable programs. They must have changed between Raspian 10 & Raspian 11. For example, in Makefile.in, there are calls to "/bin/systemctl", but on the current version of Raspian, the correct path is "/usr/bin/systemctl".
There were many path errors that I corrected with a text editor. Then it ran fine :)