Restore reproducibility
On the Release Team side, I'm working towards enforcing reproducibility in testing. Fixing castle-game-engine seems like an obvious thing to do as a team member. I don't feel involved enough anymore to just push to the master branch, hence my PR.
You can see here that fixed something (I skipped building the -src binary to enable salsa to run the reprotest pipeline): https://salsa.debian.org/elbrus/castle-game-engine/-/pipelines/975781