Bump prometheus-client-mmap to 0.9.4
Fixes failing builds with gcc on Archlinux and Ruby 2.4.4.
See https://gitlab.com/gitlab-org/prometheus-client-mmap/merge_requests/26 for more details.
Fixes failing builds with gcc on Archlinux and Ruby 2.4.4.
See https://gitlab.com/gitlab-org/prometheus-client-mmap/merge_requests/26 for more details.