Motivation for this change

Following CMakes own recommendation, we should disable the package registry in nix builds:
https://cmake.org/cmake/help/latest/manual/cmake-packages.7.html#disabling-the-package-registry

For builds were no home folder is available, the change seems to be mostly cosmetic, as it just removes warning messages, but in the opposite case the package registry would allow CMake to build against arbitrary packages in the registry.

Things done

• Tested using sandboxing (nix.useSandbox on NixOS, or option sandbox in nix.conf on non-NixOS)
• Built on platform(s)
  • NixOS
  • macOS
  • other Linux distributions
• Tested via one or more NixOS test(s) if existing and applicable for the change (look inside nixos/tests)
• Tested compilation of all pkgs that depend on this change using nix-shell -p nox --run "nox-review wip"
• Tested execution of all binary files (usually in ./result/bin/)
• Determined the impact on package closure size (by running nix path-info -S before and after)
• Assured whether relevant documentation is up to date
• Fits CONTRIBUTING.md.

First submitted against master in #54982 (just for completeness).