Investigate "No space left on device" CI error on PRs

The problem seems to happen only on the upstream repository, or
maybe only on PRs from forks. This initially makes no changes, to
verify that the problem does not simply happen regardless of
content.

See GitoxideLabs#1668, and in particular
GitoxideLabs#1668 (comment),
as well as #3, and #4, for details.