nix-shell fails on Darwin

[fricklerhandwerk]

error: nix-shell requires a single derivation
Try 'nix-shell --help' for more information.

The reason seems to be that there are x86_64-darwin outputs (similar to this issue), as x86_64-linux is hardcoded.

Hotfixing this by replacing the system string still yields:

Package ‘xidel-0.9.8’ in /nix/store/57y6djpqdmjglkdzgrbsdyjzqkn48ff1-source/pkgs/tools/text/xidel/default.nix:87 is not supported on ‘x86_64-darwin’, refusing to evaluate.

Hacking xidel into evaluating on Darwin reveals

error: Package ‘fpc-3.2.0’ in /nix/store/74wznb06asq3sls1902fbkm7ibzyvk7m-nixpkgs-21.05pre296212.530a53dcbc9/nixpkgs/pkgs/development/compilers/fpc/default.nix:44 is not supported on ‘x86_64-darwin’, refusing to evaluate.

and this is a bit of a harder nut to crack, because the fpc builder can only extract tar, but fpc Darwin binaries are packaged as dmg.

Related: NixOS/nixpkgs#108532

[garbas]

The current build tools used for nixos website don't work on MacOS, saddly. But when we select new one this will be one of the criteria.

There was some attempt to at least gave instructions how to build things with Docker on MacOS, but was abandoned due to lack of time -> #816