This commit upgrades uefiToolPackages.new-engine to the latest version
as of writing. Version A68 is now using Qt6 and no longer comes with
a custom build script, so the build logic compared to the old-engine
variant has become sufficiently divergent that I decided that it would
be easier to split them into two entirely different derivations.
Additionally, I:
- added myself as a maintainer
- added a patch that allows the new-engine variant to build on Darwin
- correctly set `mainProgram` in the old-engine variant
