gitlab-ci.yml: Replace all explicit calls to ninja with meson commands

gitlab-ci.yml: Replace all explicit calls to ninja with meson commands

This is continuation of what commit b56e2be68e3 started. If we stick to
only calling meson commands directly, we can achieve much better
consistency in passing arguments to meson especially if we unify the
recipes run in gitlab CI and what we can currently run locally in
containers using docker/podman.

Signed-off-by: Erik Skultety <eskultet@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>