`cabal-validate`: Steps change depending on options which choose steps

[9999years]

The build step will build... the stuff used by the other steps you're running!

E.g. solver-benchmarks is only built if --solver-benchmarks is passed... but if you use --step solver-benchmarks-run manually, it won't be built. cabal-install-solver will not be built if --lib-only is passed.

So this introduces two confusing behaviors:

1. ./validate.sh -s build && ./validate.sh -s solver-benchmarks will error because solver-benchmarks aren't built.
2. ./validate.sh -s build won't catch compile errors in solver-benchmarks, which is a little confusing. ./validate.sh -s build should... build everything that gets tested in CI, I think!

Related:

• cabal-validate: Too many ways to choose steps #10564
• cabal-validate: Steps are not granular enough, add groups of steps #10563

Proposal: There should be a build group which builds everything, and steps build-lib, build-cli, and build-solver-benchmarks which build specific sets of libraries.