Before this change, the final plist was made of a basic pkg-plist, plus files added through the PLIST_FILES variable in the Makefile, depending on the selected options. This didn't work for the LUA option, which require @dirrm entries.
Now, the Makefile uses PLIST_SUB, which allows to have a complete pkg-plist where some entries are commentted out when the associated option is disabled.
PR: 190516.
Tested by: Matthieu Volat <mazhe@alkumuna.eu>