Fixup PRODUCT_LUA replacement while here.

While here switch images to UFS2.

In normal build operations the variables are populated by the
environment already so the templated fallbacks are never used.

We would assume and set php= which is empty and not found.

kBuild: Generating python - /usr/obj/usr/ports/emulators/virtualbox-ose-additions-nox11/work/VirtualBox-5.2.44/out/freebsd.amd64/release/obj/VBoxOGLgen/cr_packfunctions.h
kmk_builtin_redirect: posix_spawnp(python-not-found) failed: No such file or directory
kmk: *** [/usr/obj/usr/ports/emulators/virtualbox-ose-additions-nox11/work/VirtualBox-5.2.44/out/freebsd.amd64/release/obj/VBoxOGLgen/cr_packfunctions.h] Error 10
kmk: *** Waiting for unfinished jobs....
kmk: *** Exiting with status 2
*** Error code 2

Stop.
make: stopped in /usr/ports/emulators/virtualbox-ose-additions-nox11

This request has been voiced a couple of times over the years.
With some mileage behind us it would make sense to enhance the
system with a print server that we don't offer any plugins for
or at least that is not planned from the core team side.

As with everything: use at your own risk.  ;)

fixes https://github.com/opnsense/plugins/issues/1996