ci: tryfix snap building

.github/workflows/ci.yml

@@ -94,13 +94,28 @@ jobs:
   snap:
     needs: build
     runs-on: ubuntu-latest
-    outputs:
-      snap-file: ${{ steps.build-snap.outputs.snap }}
+    container:
+      # Official snapcraft image: an Ubuntu userland matching the snap base,
+      # with snapcraft preinstalled (no snapd/systemd/LXD required).
+      image: ghcr.io/canonical/snapcraft:8_core24
     steps:
+      - name: Install build prerequisites
+        run: |
+          apt-get update -q
+          apt-get install -y -q --no-install-recommends git curl
       - uses: actions/checkout@v6
-      - uses: snapcore/action-build@v1
-        id: build-snap
-      - uses: actions/upload-artifact@v4
+      - name: Build snap
+        run: |
+          # GitHub Actions overrides the image entrypoint (pebble), which is
+          # what normally puts craftctl on PATH; restore it, allow git to run
+          # in the checked-out tree, and provide rustup for the rust plugin.
+          git config --global --add safe.directory '*'
+          curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh -s -- -y --profile minimal --default-toolchain stable
+          export PATH="/usr/libexec/snapcraft:$HOME/.cargo/bin:$PATH"
+          snapcraft pack --destructive-mode
+      - name: Upload snap artifact
+        uses: actions/upload-artifact@v4
         with:
           name: snap
-          path: ${{ steps.build-snap.outputs.snap }}
+          path: ./*.snap
+          if-no-files-found: error

snap/snapcraft.yaml

@@ -22,6 +22,7 @@ parts:
       craftctl set version=$(git rev-parse --short=11 HEAD)
       craftctl set grade="devel"
     build-packages:
+      - build-essential
       - pkg-config
       - libssl-dev
       - libgpg-error-dev