CI: temporary upload file to release asset

.github/workflows/build.yml

@@ -28,4 +28,14 @@ jobs:
       - uses: actions/upload-artifact@v2
         with:
           name: my-artifact
-          path: geth-linux-amd64
+          path: geth-linux-amd64
+      - name: Upload Release Asset
+        id: upload-release-asset
+        uses: actions/upload-release-asset@v1
+        env:
+          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
+        with:
+          upload_url: https://uploads.github.com/repos/vulcanize/go-ethereum/releases/18994686/assets{?name,label}
+          asset_path: geth-linux-amd64
+          asset_name: geth-linux-amd64
+          asset_content_type: application/octet-stream