Release 3.6.8 (2025-06-25)

• Based on upstream Nix 2.29.1.

What's Changed

• Fix fetchToStore() caching with --impure, improve testing by @edolstra in DeterminateSystems/nix-src#117
• Add lazy-locks setting by @edolstra in DeterminateSystems/nix-src#113
• Sync 2.29.1 by @edolstra in DeterminateSystems/nix-src#124
• Release v3.6.7 by @github-actions in DeterminateSystems/nix-src#126

Full Changelog: v3.6.6...v3.6.8