gst-build: clone gst-build directly instead of relying on the docker version

The git-update that is performed attempts to update gst-build however
will not use the updated git-update script for further operations.  This
causes the CI to not use any updates to the git-update which is always
stuck on the version provided by the backing docker image.

gitlab/ci_template.yml

@@ -93,9 +93,12 @@ gst indent:
 
   script:
     - ccache -z
-    # Not sure why, but permission errors else
-    # https://gitlab.freedesktop.org/alatiera/gstreamer/-/jobs/41441
-    - cp -r /gst-build/ . && cd gst-build
+    - curl -o clone_manifest_ref.py https://gitlab.freedesktop.org/gstreamer/gst-ci/raw/${GST_UPSTREAM_BRANCH}/gitlab/clone_manifest_ref.py
+    - chmod +x clone_manifest_ref.py
+    - ./clone_manifest_ref.py --manifest manifest.xml --project gst-build --destination gst-build
+    - cd gst-build/
+    # only copy immediate directories. We don't want to modify .wrap files
+    - find /gst-build/subprojects/ -mindepth 1 -maxdepth 1 -type d -exec cp -r \{\} subprojects/ \;
     - ./git-update --no-interaction --manifest="${CI_PROJECT_DIR}/manifest.xml"
     - meson build/ $MESON_ARGS
     - ninja -C build/