Add isLegacy flake schema output attribute#381

edolstra wants to merge 5 commits intomainDeterminateSystems/nix-src:mainfrom

eelcodolstra/nix-334-nix-flake-check-fix-legacypackages-handlingDeterminateSystems/nix-src:eelcodolstra/nix-334-nix-flake-check-fix-legacypackages-handlingCopy head branch name to clipboard