[CI] Run git gc when creating a repo cache (#17368)

Without this cached checkout is slow.

Note this is only when we re-create the cache, which only happens if it
got deleted/doesn't exist for some reason.

Signed-off-by: Sarnie, Nick <[email protected]>

Author: sarnex

devops/actions/cached_checkout/action.yml

@@ -34,6 +34,7 @@ runs:
         git pull --prune
       else
         git clone https://github.com/${{ inputs.repository }}.git .
+        git gc
       fi
   - name: Checkout
     env: