ci: nix-store --realise to tools:

Since we're building only tools now, we can just specify them directly
in the `tools:` parameter of `setup-nix` action.

.github/workflows/ci.yaml

@@ -27,13 +27,7 @@ jobs:
  uses: ./.github/actions/setup-nix
  with:
  cache-id: common
- - name: Put all tools to store to be cached afterwards
- run: |
- # shellcheck disable=SC2046
- nix-store -v --realize $( nix-instantiate default.nix \
- -A style -A withTools -A memory -A tests -A release \
- )
- shell: bash
+ tools: style withTools memory tests release
 
  Lint-Style:
  name: Lint & check code style