No support for aarch64 darwin via flakes

[sambacha]

I know the status of dapptools is in maintenance mode, I open this issue to see if you would accept a PR to fix this for Apple Silicon hardware

flake 'github:dapphub/dapptools' does not provide attribute 'packages.aarch64-darwin.dapp', 'legacyPackages.aarch64-darwin.dapp' or 'dapp'

Cheers

[yihuang]

We workaround it with --system x86_64-darwin and rosetta.