GitLab

Every time a head.hackage CI job is assigned to the gitlab-ci-linux-x86-64-2 runner, it will fail with the following error message (example):

$ nix-build ./ci -j$CPUS --no-build-output # collapsed multi-line command
error: configuration setting 'max-jobs' should be 'auto' or an integer
Try 'nix-build --help' for more information.

It appears that $CPUS isn't being expanded for some reason. Other runners do not appear to suffer from this issue, so a workaround is to restart the job and pray that it isn't assigned to gitlab-ci-linux-x86-64-2. This is tedious, however, and shouldn't be necessary.