perf: run make recipes in parallel during backward compat check

mentioned in commit gitaly@fd261581

mentioned in commit gitlab-pages@4a86b4aa

mentioned in commit container-registry@0784535a

mentioned in commit gitaly@ecbfab8a

mentioned in commit gitlab-pages@7162c427

mentioned in commit gitlab-shell@4f53088e

mentioned in commit container-registry@94151029

mentioned in commit gitlab@2895a822

mentioned in merge request gitlab-shell!668 (merged)

mentioned in commit container-registry@8ad5b675

mentioned in merge request gitlab!92372 (merged)

mentioned in commit gitlab@8389701e

mentioned in commit gitlab-pages@77220ca9

mentioned in merge request release-tools!1937 (merged)

mentioned in merge request gitlab-com/gl-infra/cmbr!71 (merged)

mentioned in merge request gitaly!4730 (closed)

mentioned in commit gitaly@f011de34

mentioned in commit gitaly@ea2fbc00

mentioned in commit gitaly@bf40a75a