[retro-gtk/build-doc] ci: Install glib2-doc

[Adrien Plazas <aplazas src gnome org>]

commit b168d78b334863271999099c36997891220e7bb6
Author: Adrien Plazas <kekun plazas laposte net>
Date:   Mon Apr 13 13:33:27 2020 +0200

    ci: Install glib2-doc

 .gitlab-ci.yml | 2 ++
 1 file changed, 2 insertions(+)
---
diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index 31e4b5a..e879305 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -72,6 +72,8 @@ reference:
   stage: build
   variables:
     MESON_ARGS: "--buildtype=release --libdir=lib -Dpulseaudio=disabled -Dintrospection=false 
-Dbuild-tests=false -Dbuild-doc=true"
+  before_script:
+    - dnf install -y glib2-doc
   script:
     - meson ${MESON_ARGS} _build
     - ninja -C _build