CI: Fetch gettext & ModemManager from distro

I'm not sure why we were building these from sources.
3 jobs for wip/fix-ci in 2 minutes and 31 seconds (queued for 1 second)
Status Job ID Name Coverage
  Test
passed #25062
ubuntu-16.04

00:02:21

passed #25063
ubuntu-17.10

00:02:31

passed #25064
ubuntu-18.04

00:02:11