ci: Switch from Debian unstable to Fedora 30

Fedora has GLib ≥2.60.1, which we’ll need in an upcoming commit.

Signed-off-by: Philip Withnall <withnall@endlessm.com>

.gitlab-ci.yml

@@ -1,12 +1,11 @@
-image: debian:unstable
+image: fedora:30
 
 before_script:
-  - apt update -qq
-  - apt install -y -qq build-essential meson pkg-config gtk-doc-tools
-                       libxml2-utils gobject-introspection
-                       libgirepository1.0-dev libglib2.0-dev
-                       gettext libdbus-1-dev libpolkit-gobject-1-dev git
-                       policykit-1 lcov
+  - dnf install -y meson pkgconf-pkg-config gtk-doc
+                   libxml2-devel dbus-daemon
+                   glib2-devel dbus-devel gobject-introspection-devel
+                   gettext-devel polkit-devel polkit-gnome git
+                   lcov
   - export LANG=C.UTF-8
 
 stages:
@@ -17,7 +16,7 @@ cache:
   paths:
     - _ccache/
 
-debian-unstable:
+fedora:
   stage: build
   except:
     - tags