I was able to get past my error by removing libgphoto2-dev from the development installs list, and then manually pulling/building the latest libgphoto2 from sourceforge.
…then update_indi_drivers worked.
…then, slewing to a target with my CGEM-II Wi-Fi worked!
(At least, it worked in my living room according to KStars, and it looks like the mount might be pointing the right way).
It still hits the soft stop when rotating eastward… when I don’t have the hand controller plugged in.