Add improved Nix CI workflow

.github/workflows/nix.yml

@@ -0,0 +1,53 @@
+name: Nix CI
+
+on:
+  pull_request:
+  push:
+
+jobs:
+  matrix:
+    name: Generate matrix
+    runs-on: ubuntu-latest
+    outputs:
+      matrix: ${{ steps.gen-matrix.outputs.matrix }}
+
+    steps:
+      - name: Checkout repo
+        uses: actions/checkout@v3
+
+      - name: Install Nix
+        uses: DeterminateSystems/nix-installer-action@v4
+
+      - name: Genrate matrix
+        id: gen-matrix
+        run: |
+          echo "matrix=$(nix eval --impure --json --expr '(import ./constants.nix).ghcVersions')" \
+            >> $GITHUB_OUTPUT
+
+  build:
+    needs: matrix
+    runs-on: macos-latest
+
+    strategy:
+      fail-fast: false
+      matrix:
+        ghc:  ${{ fromJson(needs.matrix.outputs.matrix) }}
+
+    name: Nix build (${{ matrix.ghc }})
+
+    steps:
+      - name: Checkout repo
+        uses: actions/checkout@v3
+
+      - name: Install Nix
+        uses: DeterminateSystems/nix-installer-action@v4
+
+      - name: Setup cache
+        uses: DeterminateSystems/magic-nix-cache-action@main
+
+      - name: Build and test
+        run: |
+          NAME=$(nix eval --impure --raw --expr '(import ./constants.nix).name')-${{ matrix.ghc }}
+          nix -L build .#$NAME
+          nix run .#$NAME -- domains
+