[pango/family-face-api] ci: Install diff

[Matthias Clasen <matthiasc src gnome org>]

commit dca93a4296eaf11b9146dfb083f214af218d23bd
Author: Matthias Clasen <mclasen redhat com>
Date:   Thu Oct 31 18:40:34 2019 -0400

    ci: Install diff
    
    Our tests are using it.

 .gitlab-ci.yml | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)
---
diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index 3758c576..b91fd650 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -23,7 +23,8 @@ gnome-runtime-linux:
         abattis-cantarell-fonts \
         google-droid-sans-fonts \
         thai-scalable-waree-fonts \
-        desktop-file-utils
+        desktop-file-utils \
+        diffutils
   script:
     - meson _build
     - ninja -C _build