Add nix flake check to CI

Author: JosephGoulden

.github/workflows/build.yml

@@ -43,3 +43,19 @@ jobs:
         run: cargo check --release
       - name: Cargo check doc on Rust ${{ matrix.toolchain }}
         run: cargo doc --release
+  check-flake:
+    name: Check Nix Flake
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: true
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v4
+      - name: Check Nix flake inputs
+        uses: DeterminateSystems/flake-checker-action@v8
+      - name: Install Nix
+        uses: cachix/install-nix-action@v31
+        with:
+          nix_path: nixpkgs=channel:nixos-25.05
+      - name: Check flake
+        run: nix flake check