feat: add action to build and upload sparse

.gitea/workflows/build-artifacts.yaml

@@ -0,0 +1,22 @@
+name: Build sparse 0.5 without FreeBSD support
+on:
+  push:
+    branches:
+      - flake
+
+jobs:
+  build-and-upload:
+    runs-on: native
+    steps:
+      - name: check out repository code
+        uses: actions/checkout@v4
+
+      - name: Build flake
+        run: |
+          /run/current-system/sw/bin/nix build .#sparse-05-client
+
+      - name: Upload resulting binary
+        uses: actions/upload-artifact@v4
+        with:
+          name: sparse-05-client
+          path: result/bin/sparse-05-client