ci: Ignore a ‘dubious ownership’ warning when updating submodules

It’s irrelavent.

Signed-off-by: Philip Withnall <pwithnall@endlessos.org>

.gitlab-ci.yml

@@ -61,6 +61,7 @@ variables:
   extends: .only-default
   before_script:
    - rm -rf subprojects/gvdb
+   - git config --global --add safe.directory $(pwd)
    - git submodule update --init --depth 1
   variables:
     GIT_SUBMODULE_STRATEGY: "none"