GH Workflow that runs "nix flake check"

.github/workflows/nix-flake-check.yaml

@@ -0,0 +1,46 @@
+name: "Check the Nix Flake using `nix flake check`"
+
+env:
+  ALLOWED_URIS: "https://github.com https://api.github.com"
+  TRUSTED_PUBLIC_KEYS: "cache.nixos.org-1:6NCHdD59X431o0gWypbMrAURkbJ16ZPMQFGspcDShjY= hydra.iohk.io:f/Ea+s+dFdN+3Y/G+FDgSq+a5NEWhJGzdjvKNGv0/EQ="
+  SUBSTITUTERS: "https://cache.nixos.org/ https://cache.iog.io"
+  REGISTRY: ghcr.io
+  IMAGE_NAME: ${{ github.repository }}
+
+on:
+  pull_request:
+  push:
+    branches:
+      - main
+
+jobs:
+  nix-flake-check:
+    name: "Run nix flake check on ${{ matrix.os }}"
+    strategy:
+      fail-fast: false
+      matrix:
+        os: [macos-14, macos-15-intel, ubuntu-22.04]
+    runs-on: ${{ matrix.os }}
+    steps:
+    - name: 📥 Checkout repository
+      uses: actions/checkout@v4
+    - name: Free Disk Space (Ubuntu)
+      if: matrix.os == 'ubuntu-22.04'
+      uses: jlumbroso/free-disk-space@main
+      with:
+        tool-cache: true
+    - name: 🛠️ Install Nix
+      uses: cachix/install-nix-action@v21
+      with:
+        nix_path: nixpkgs=channel:nixos-unstable
+        install_url: https://releases.nixos.org/nix/nix-2.18.8/install
+        extra_nix_config: |
+          allowed-uris = ${{ env.ALLOWED_URIS }}
+          trusted-public-keys = ${{ env.TRUSTED_PUBLIC_KEYS }}
+          substituters = ${{ env.SUBSTITUTERS }}
+          experimental-features = nix-command flakes
+          accept-flake-config = true
+    - name: nix-flake-check
+      run: |
+        nix show-config
+        nix --show-trace -L flake check

flake.nix

@@ -56,14 +56,15 @@
         "aarch64-darwin"
       ];
 
+      # TODO(bladyjoker): Enable when Hydra is back to stable
       flake.hydraJobs = import ./nix/hydra.nix {
         flake = self;
         inherit lib;
         systems = [
           "x86_64-linux"
-          "x86_64-darwin"
-          "aarch64-linux"
-          "aarch64-darwin"
+          # "x86_64-darwin"
+          # "aarch64-linux"
+          # "aarch64-darwin"
         ];
       };