Cleaner build system (#187)

[gabrielhdt]

• Use Nixpkg's GHC 8.10.7

Also provide a flake for reproducibility with

• a default shell suitable for development (hls and stuff)

• a ci shell accessible with nix develop .#ci which doesn't have development related dependencies

• CI tweaks

• Put tests that don't require internet (i.e. ormolu and hpack) into the flake checks

• Some sanity on the script 'run-tests' (advised by shellcheck)

• Update github actions dependencies

• Update github caching

• Removed shell.nix

Tuned the setup of LD_LIBRARY_PATH

• Activate flake check in CI, fix formatting

• Add dependabot

• Replace cache by artifacts for test output

• Checks exit on error

• Remove envrc

Don't enforce an envrc, let people choose theirs :)

• Bump version of Pirouette

• Add Z3 as a dynamic library

• Also add Z3 to buildInputs

• Add dependabot

• Renaming workflows and steps, removed action

The run nix action was not used.

Co-authored-by: Nicolas “Niols” Jeannerod nicolas.jeannerod@tweag.io