Hi,
Sorry I can't answer your question directly, I'm not sure what is going on there.
I haven't tried this in over a year, but there's a chance it might work for you if you'd like to try this installer script. At a minimum it shows the steps Rob used to obtain GSC in his scripts. github.com/JerryBlack/buildKstarsNightly...b/main/installgsc.sh
Cheers