Fix CircleCI builds

I don't know why, but it fails to fetch submodules...

.circleci/config.yml

@@ -28,6 +28,8 @@ shared:
       name: Initialize
       command: |
         mkdir -p /tmp/artifacts
+        # Workaround for failing submodule fetching
+        git config --global --unset url."ssh://git@github.com".insteadOf || true
 
   # Commmon environment variables
   common_environment: &common_environment