Update dune build with latest opam packages #4

	name: Build

	on:
	- push
	- pull_request
	- workflow_dispatch

	jobs:
	build-and-test:
	strategy:
	fail-fast: false
	matrix:
	os:
	- ubuntu-latest
	# - macos-latest
	# - windows-latest # zarith fails to build on Windows
	ocaml-compiler:
	- "5.2"

	runs-on: ${{ matrix.os }}

	steps:
	- name: Checkout tree
	uses: actions/checkout@v4

	- name: Set-up OCaml
	uses: ocaml/setup-ocaml@v3
	with:
	ocaml-compiler: ${{ matrix.ocaml-compiler }}

	- name: Cache opam root
	uses: actions/cache@v4
	with:
	path: ~/.opam
	key: opam-root-${{ runner.os }}-ocaml-${{ matrix.ocaml-compiler }}-${{ hashFiles('flake.nix') }}

	# - name: Cache opam switch
	# id: cache-opam-packages
	# uses: actions/cache@v4
	# with:
	# path: switch-state.tar.gz
	# key: opam-cache-${{ runner.os }}-ocaml-${{ matrix.ocaml-compiler }}-${{ hashFiles('flake.nix') }}

	# - name: Install cached opam packages
	# if: steps.cache-opam-packages.outputs.cache-hit == 'true'
	# run: \|
	# opam init --disable-sandboxing -y
	# eval $(opam env)
	# opam switch create . --deps-only --locked -y \|\| opam switch import switch-state.tar.gz

	- name: Install opam packages # (uncached)
	# if: steps.cache-opam-packages.outputs.cache-hit != 'true'
	run: opam install coq dune

	- name: Dune build
	run: opam exec -- dune build

	# - name: Export opam switch
	# if: steps.opam-cache.outputs.cache-hit != 'true'
	# run: \|
	# eval $(opam env)
	# opam switch export switch-state.tar.gz

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