Adds explicit "systems" input to flake.nix #450

	name: ci-linux
	on:
	push:
	branches:
	- main
	pull_request:

	concurrency:
	group: ${{ github.ref }}
	cancel-in-progress: true

	jobs:
	build:
	runs-on: ubuntu-latest
	steps:
	# install deps.
	- name: install dependencies
	run: \|
	sudo apt-get update
	sudo apt-get install -y libsystemd-dev

	- name: Install system dependencies
	uses: input-output-hk/actions/base@latest

	- uses: haskell-actions/setup@v2
	id: cabal-setup
	with:
	ghc-version: '9.6.6'
	cabal-version: '3.10.3.0'

	- uses: actions/checkout@v4

	- name: Cache .cabal
	uses: actions/cache@v3
	with:
	path: ${{ steps.cabal-setup.outputs.cabal-store }}
	key: cabal-${{ hashFiles('cabal.project') }}

	- name: build & test
	run: \|
	cabal update
	cabal build -j all --enable-tests
	cabal test all

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