Ensure git doesn't duplicate binary files

What does this MR do?

Ensures git is using symlinks rather than hardlinks. Otherwise the hardlinks are being turned into duplicates during asset moving.

Fixes: gitlab-org/charts/gitlab#3274 (closed)

There is also a MR to fix this upstream: gitlab-org/gitaly!4511 (closed) if that gets merged this one isn't necessary. Also there are other options in this repo that fixes the filesize problem: !997 (merged)

But we can use this fix if we want to fix the pipelines quickly.

Checklist

See Definition of done.

For anything in this list which will not be completed, please provide a reason in the MR discussion

Required

• Merge Request Title, and Description are up to date, accurate, and descriptive
• MR targeting the appropriate branch
• MR has a green pipeline on GitLab.com

Expected (please provide an explanation if not completing)

• Test plan indicating conditions for success has been posted and passes
• Documentation created/updated
• Integration tests added to GitLab QA
• The impact any change in container size has should be evaluated