Two changes in separate commits, please review them one at a time to make it clearer.
Speed up projectenv.sh generation and execution: moved to !3824 (merged) Improve projectenv.sh generation for super-project builds by populating extra_commands only once (needs cmake 3.19). Use a faster shell-based duplicate removal.
- Speed up projectenv.sh by removing duplicates at the source. This is more controversial, it might interfere with !3159 (merged), but since I don't really understand it, @clemenci I need your help. In particular, it would be good to note down what is the reason to "override GaudiToolbox internal macro to use lhcb_env".