add test for force_rebuild (#448)

see also [forgejo/runner #406](https://code.forgejo.org/forgejo/runner/pulls/406)

Reviewed-on: https://code.forgejo.org/forgejo/end-to-end/pulls/448
Reviewed-by: earl-warren <earl-warren@noreply.code.forgejo.org>
Co-authored-by: gratux <gratux@noreply.code.forgejo.org>
Co-committed-by: gratux <gratux@noreply.code.forgejo.org>

actions/example-force-rebuild/runner-config-with-rebuild.yml

@@ -0,0 +1,30 @@
+log:
+  level: debug
+
+runner:
+  file: .runner
+  capacity: 1
+  env_file: .env
+  timeout: 3h
+  insecure: false
+  fetch_timeout: 5s
+  fetch_interval: 2s
+  labels: ["docker:docker://code.forgejo.org/oci/node:20-bookworm"]
+
+cache:
+  enabled: false
+  dir: ""
+  host: ""
+  port: 0
+
+container:
+  network: "bridge"
+  privileged: false
+  options:
+  workdir_parent:
+  valid_volumes: ["/srv/example"]
+  docker_host: ""
+  force_rebuild: true
+
+host:
+  workdir_parent: