The Makefile does not support macOS any more

The getent command is used in the Makefile to retrieve the numerical GID of the docker group. macOS does not provide the getent command. Fortunately this is not needed because Docker Desktop on macOS is installed with the GID of the user who installed it.

Solution: Split up the retrieval of the numerical GID into Linux or macOS, like is already done for the DISPLAY variable. On Linux do it the way it was, on macOS simply assign id -g.