`ghc-8.10.4` not supported on `aarch64-darwin` (Apple Silicon)

```log
m1:~ $ echo $NIXPKGS_ALLOW_UNSUPPORTED_SYSTEM
1
m1:~ $ curl https://dapp.tools/install | sh
% Total % Received % Xferd Average Speed Time Time Time Current
Dload Upload Total Spent Left Speed
100 857 100 857 0 0 4570 0 --:--:-- --:--:-- --:--:-- 4708
Configured https://dapp.cachix.org binary cache in ~/.config/nix/nix.conf
error: Package ‘ghc-8.10.4’ in /nix/store/wgjf744s860krnci5g5qwlcdsrf1d7iy-nixpkgs-release-21.05/pkgs/development/compilers/ghc/8.10.4.nix:254 is not supported on ‘aarch64-darwin’, refusing to evaluate.

a) To temporarily allow packages that are unsupported for this system, you can use an environment variable
for a single invocation of the nix tools.

$ export NIXPKGS_ALLOW_UNSUPPORTED_SYSTEM=1

b) For `nixos-rebuild` you can set
{ nixpkgs.config.allowUnsupportedSystem = true; }
in configuration.nix to override this.

c) For `nix-env`, `nix-build`, `nix-shell` or any other Nix command you can add
{ allowUnsupportedSystem = true; }
to ~/.config/nixpkgs/config.nix.

(use '--show-trace' to show detailed location information)
All set!
```

I'm on macOS Monterey 12.0 Beta (21A5543b)