Build system in docs + AUR package deviates from build_all.sh

Hi there @bigbigmdm! I received a patch via email and LinkedIn message from @AndreiCherniaev regarding a change in the build system and that the AUR package should be updated to match. The AUR package currently builds using similar commands to the README; however, I can update this to match the cmake-only flow in [build_all.sh](https://github.com/bigbigmdm/IMSProg/blob/main/build_all.sh). I haven't received any reports of the current package failing to build, but I'm happy to change the AUR package for the next version if this is desired, leave it if not, and perhaps the README/script should be updated for consistency? Thanks! :)