so far there is no stat, but I will add one in the futur to simplify that one. Actually there is the lfs lua package which I plan to import, but for capsicumisation I have to modify some function first. So in the meantime it does the trick.
The function os.remove is equivalent of remove(3) and behave the same, so it removes the symlink: https://github.com/freebsd/pkg/blob/master/libpkg/lua_scripts.c#L166
Basically the behaviour is the same as [ -s ... ] && rm -f
Wouldn't it be interesting to have this only work on a regular file, it does not make much sense if it was tried on a symlink.
(Maybe I am trying to hard to find stupid things people will do.)