Install script can't find diskutil because the diskutil not in $PATH

Steps To Reproduce

1. Install macOS Big Sur 11.2
2. Run the installation command:

curl -L https://nixos.org/nix/install | sh

3. See error:

...unpack/nix-2.3.10-x86_64-darwin/install: line 115: diskutil: command not found
-:1: parser error : Document is empty

I think the solution is to call diskutil by its full path: /usr/sbin/diskutil.