I understand why it might look like that to you as I only shared a small excerpt from the terminal as it was running the script. But I can assure you it is indicative of GSC not being compiled. I believe it says GSC is already installed due to it having been present before the upgrade to Bullseye, and the fact that the images produced by the simulator are currently corrupted.
And I also see no new build directory for GSC. Furthermore I saw PHD2 compile properly, and it runs fine.
Maybe there are also some other things I need to clean up first.