Incompatible with Cabal Nix-style local builds

[Bo98]

Cabal has a new build system: https://cabal.readthedocs.io/en/latest/nix-local-build-overview.html and it is now the default as of Cabal 3.0.

As such, the arx build scripts no longer work on Cabal 3.0. A quick fix is to use the v1- prefix in the build commands but do note that the v1 commands are deprecated and will be removed altogether in the future.

[chenrui333]

@solidsnack, ping.