Set up a nix build job

.gitea/workflows/actions.yaml

@@ -17,3 +17,14 @@ jobs:
         run: |
           ls ${{ gitea.workspace }}
       - run: echo "This job's status is ${{ job.status }}."
+
+  build-flake:
+    runs-on: native
+    steps:
+      - name: Checkout repository code
+        uses: actions/checkout@v4
+      - name: Build the apps
+        run: nix build .#all
+      - name: Check the end of the build
+        run: ls ${{ gitea.workspace }}/result/bin
+