Upgrade to gitlab-ci 0.6.0 module system
Summary
Upgrade to gitlab-ci 0.6.0 with new modular structure.
Changes
- Update gitlab-ci from 0.5.0 to 0.6.0
- Update nix/ci.nix to use new modular import structure
- Import omnix and cachix modules explicitly
- Configure systems from horizon.systems.ci.targets
Breaking Changes in gitlab-ci 0.6.0
- The
systemsoption is now required (no default value) - This makes it explicit where systems come from