Fix building and attaching release artifacts (#17921)

Broke in #17905 due to upgrading the `upload-artifact` action, as we
didn't rename debs. I think we also need to change how we download the
artefacts and attach them to a release, as they'll download to a
different place.

Docs:
- https://github.com/actions/upload-artifact/tree/v4/
- https://github.com/actions/download-artifact/tree/v4/

.github/workflows/release-artifacts.yml

@@ -91,10 +91,19 @@ jobs:
           rm -rf /tmp/.buildx-cache
           mv /tmp/.buildx-cache-new /tmp/.buildx-cache
 
+      - name: Artifact name
+        id: artifact-name
+        # We can't have colons in the upload name of the artifact, so we convert
+        # e.g. `debian:sid` to `sid`.
+        env:
+          DISTRO: ${{ matrix.distro }}
+        run: |
+          echo "ARTIFACT_NAME=${DISTRO#*:}" >> "$GITHUB_OUTPUT"
+
       - name: Upload debs as artifacts
         uses: actions/upload-artifact@v4
         with:
-          name: debs
+          name: debs-${{ steps.artifact-name.outputs.ARTIFACT_NAME }}
           path: debs/*
 
   build-wheels:
@@ -196,15 +205,20 @@ jobs:
       - name: Download all workflow run artifacts
         uses: actions/download-artifact@v4
       - name: Build a tarball for the debs
-        run: tar -cvJf debs.tar.xz debs
+        # We need to merge all the debs uploads into one folder, then compress
+        # that.
+        run: |
+          mkdir debs
+          mv debs*/* debs/
+          tar -cvJf debs.tar.xz debs
       - name: Attach to release
         uses: softprops/action-gh-release@a929a66f232c1b11af63782948aa2210f981808a  # PR#109
         env:
           GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
         with:
           files: |
             Sdist/*
-            Wheel/*
+            Wheel*/*
             debs.tar.xz
           # if it's not already published, keep the release as a draft.
           draft: true

changelog.d/17921.misc

@@ -0,0 +1 @@
+Fix building and attaching release artifacts during the release process.