Merge branch 'gitlab-runner-community' into 'master'

dockerfile: install gitlab-runner-helper from community

See merge request !3
3 jobs for enable-x86 in 27 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Build
passed #442
docker-alpine s390x
build-s390x

00:00:20

passed #444
docker-alpine x86
build-x86

00:00:26

passed #443
docker-alpine x86_64
build-x86_64

00:00:26