NixOS install broken on Mac OS Catalina

[sethfork]

This affects the dapptools install script, as well as the install script from nixos.

See NixOS/nix#2925

[xmxanuel]

I upgraded to MacOS Catalina and fixed dapptools by creating a APFS volume for nix as a workaround.

described here by @callahad
NixOS/nix#2925 (comment)

I followed step 1 and step 2 and afterwards just copied my existing nix folder (new path in Catalina) to /nix

sudo chown -R $(whoami) /nix
cp -a /Users/Shared/Relocated\ Items/Security/nix/* /nix/

(nix copy in /Users/Shared/... can be removed afterwards)

After that: dapp worked again.