github-ci: add a nix build

This will test that shell.nix is working properly and also
test compile-commands Makefile target.

Author: regit

.github/workflows/nix.yml

@@ -0,0 +1,19 @@
+name: "Nix Env Build"
+on:
+  pull_request:
+  push:
+jobs:
+  tests:
+    runs-on: ubuntu-latest
+    steps:
+    - uses: actions/checkout@v4
+    - uses: cachix/install-nix-action@v31
+      with:
+        nix_path: nixpkgs=channel:nixos-24.11
+    - run: nix-shell --run ./scripts/bundle.sh
+    - run: nix-shell --run ./autogen.sh
+    - run: nix-shell --run ./configure
+    - run: nix-shell --run make
+    - run: nix-shell --run "src/suricata -V"
+    - run: nix-shell --run "make compile-commands"
+    - run: nix-shell --run "make compile-commands"