Add scheduled GitLab CI jobs.

4 jobs for <span class="ref-name">feature/add-scheduled-gitlab-ci-jobs</span> in 12 minutes and 59 seconds (queued for 3 seconds)
Status Job ID Name Coverage
  Test
passed #4629
docker
job-debian9-ninja-clang

00:00:52

passed #4628
docker
job-debian9-ninja-gcc

00:00:47

passed #4630
macosx
job-macosx-ninja

00:09:50

passed #4631
windows
job-windows-vs2015

00:12:06