On a fresh Mac, you'll need to install Xcode Command Line Tools which includes git and other essential development tools:
xcode-select --install
git clone https://github.com/robgordon89/nix-config.nix
curl --proto '=https' --tlsv1.2 -sSf -L https://install.determinate.systems/nix | sh -s -- install --no-confirm
nix develop
task build
task build
task update