chore: do not needlessly upload an artifact when there is no build (#916)

- ${{ needs.build.outputs.built }} is true if there is a build from source, false otherwise
- prepare-end-to-end local action does not attempt to download an artifact if inputs.built  is false

Reviewed-on: https://code.forgejo.org/forgejo/end-to-end/pulls/916
Reviewed-by: Gusted <gusted@noreply.code.forgejo.org>
Co-authored-by: Earl Warren <contact@earl-warren.org>
Co-committed-by: Earl Warren <contact@earl-warren.org>

.forgejo/prepare-end-to-end/action.yml

@@ -1,3 +1,7 @@
+inputs:
+  built:
+    description: 'True if a source build is available, false otherwise'
+
 runs:
   using: "composite"
   steps:
@@ -16,6 +20,7 @@ runs:
           install-only: true
       - run: forgejo-binary.sh ensure_user forgejo
       - uses: actions/download-artifact@v3
+        if: ${{ inputs.built == true }}
         with:
           name: forgejo-dev
           path: /srv/forgejo-binaries