Create a cabal.project file and make the build "non-stateful"

Problem

Currently, to compile the frontend, the user has to manually clone and install the curry-base package, since this project depends on a newer version (1.2.0) than the latest version from Hackage (1.1.1).

Motivation

Since Cabal ist moving towards non-stateful, reproducible builds with version 2 (see here), it would be nice to have this package "just build" when running cabal v2-build, without any preliminary steps.

Additionally, a non-stateful build could enable automatic CI builds/deployments, if so desired, in the future.

Solution

Adding a cabal.project file that declares a source-repository-package (as introduced by Cabal 2.4, see here) pointing towards the curry-base repository would fix the issue, since Cabal could automatically download and build curry-base from source.