This diff will adapt number of jobs depending on the CI_RUNNER_DESCRIPTION

So we can have -j 12 and -j 64 in the same .gitlab-ci.yml ! :)

I can configure the runner to have higher concurrency, because in the config file /etc/gitlab-runner/config.toml I have right now:

concurrent = 1

But I could set for example concurrent = 2 and we would use -j 32 instead.

Which we prefer?