Sync GDK log files when running gdk update/reconfigure

What does this merge request do and why?

When running gdk update or gdk reconfigure we show a spinner and redirect the output to log/gdk/.

However, the output is buffered so long-running steps cannot be inspected via tail -f log/gdk/rake-<timestamp>/<task>.log. It's mostly empty until the OS or Ruby flushes buffers.

This commit ensure that logfiles have "sync mode" enabled.

How to set up and validate locally

1. mise uninstall ruby@3.3.7
2. gdk reconfigure
3. tail -f log/gdk/rake-<most recent timestamp>/reconfigure-make-gitlab-http-router-setup.log
4. See live updates - it's no longer buffered

Impacted categories

The following categories relate to this merge request:

• gdk-reliability - e.g. When a GDK action fails to complete.
• gdk-usability - e.g. Improvements or suggestions around how the GDK functions.
• gdk-performance - e.g. When a GDK action is slow or times out.

Merge request checklist

• This change is backward compatible. If not, please include steps to communicate to our users.
• Tests added for new functionality. If not, please raise an issue to follow-up.
• Documentation added/updated, if needed.
• Announcement added, if change is notable.
• gdk doctor test added, if needed.