gitlab-runner-helper: use default umask
scripts/gitlab-runner-helper sets umask to 0000 to fix issues where ci jobs would be running as a different user, preventing access to files.
This causes issues when files in repositories end up in build artifacts with world writable permissions.
One such example is the alpine-gitlab-ci project where
ends up word-writable, preventing sudo to work.
Set it to the standard 0022 to fix this issue.