ci: more work

Author: thomasjm

.github/workflows/ci.yml

@@ -12,19 +12,12 @@ jobs:
       fail-fast: false
 
     steps:
-    # - name: Install libraries
-    #   run: |
-    #     sudo apt update
-    #     sudo apt install -y libzmq5-dev libpcre3-dev
-
     - uses: actions/checkout@v6
 
-    # - uses: haskell/actions/setup@v1
-    #   name: Setup Haskell Stack
-    #   with:
-    #     ghc-version: ${{ matrix.ghc }}
-    #     stack-version: "latest"
-    #     enable-stack: true
+    - uses: cachix/install-nix-action@v31
+      with:
+        nix_path: nixpkgs=channel:nixos-unstable
+    - uses: DeterminateSystems/magic-nix-cache-action@main
 
     - uses: actions/cache@v5
       name: Cache ~/.stack
@@ -47,38 +40,34 @@ jobs:
         nix run .#stack -- test --nix --test-arguments --print
 
   no-gmp:
-    runs-on: [self-hosted, Linux, desktop]
+    runs-on: ubuntu-latest
     strategy:
       fail-fast: false
     steps:
-    - uses: actions/checkout@v4
+    - uses: actions/checkout@v6
 
-    # - uses: cachix/install-nix-action@v22
-    #   with:
-    #     nix_path: nixpkgs=channel:nixos-unstable
-    #     extra_nix_config: |
-    #       trusted-public-keys = hydra.iohk.io:f/Ea+s+dFdN+3Y/G+FDgSq+a5NEWhJGzdjvKNGv0/EQ= cache.nixos.org-1:6NCHdD59X431o0gWypbMrAURkbJ16ZPMQFGspcDShjY=
-    #       substituters = https://hydra.iohk.io https://cache.nixos.org/
+    - uses: cachix/install-nix-action@v31
+      with:
+        nix_path: nixpkgs=channel:nixos-unstable
+    - uses: DeterminateSystems/magic-nix-cache-action@main
 
     - name: No GMP
       run: |
         nix run .#verify-no-gmp
 
   nix:
     name: Nix
-    runs-on: [self-hosted, Linux, desktop]
+    runs-on: ubuntu-latest
     strategy:
       fail-fast: false
 
     steps:
-    - uses: actions/checkout@v4
+    - uses: actions/checkout@v6
 
-    # - uses: cachix/install-nix-action@v22
-    #   with:
-    #     nix_path: nixpkgs=channel:nixos-unstable
-    #     extra_nix_config: |
-    #       trusted-public-keys = hydra.iohk.io:f/Ea+s+dFdN+3Y/G+FDgSq+a5NEWhJGzdjvKNGv0/EQ= cache.nixos.org-1:6NCHdD59X431o0gWypbMrAURkbJ16ZPMQFGspcDShjY=
-    #       substituters = https://hydra.iohk.io https://cache.nixos.org/
+    - uses: cachix/install-nix-action@v31
+      with:
+        nix_path: nixpkgs=channel:nixos-unstable
+    - uses: DeterminateSystems/magic-nix-cache-action@main
 
     - name: Build
       run: |