builder image: use sane umask

Open username-removed-163557 requested to merge glensc/gitlab-ci-multi-runner:patch-6 into master

What does this MR do?

Revert umask 0000 to umask 0002

Why was this MR needed?

Are there points in the code the reviewer needs to double check?

Does this MR meet the acceptance criteria?

  • Documentation created/updated
  • Tests
    • Added for this feature/bug
    • All builds are passing
  • Branch has no merge conflicts with master (if you do - rebase it please)

What are the relevant issue numbers?

Closes: #1736

Edited by username-removed-163557