[gnome-flashback] ci: add back extra coverity dependencies

[Alberts Muktupāvels <muktupavels src gnome org>]

commit 3bef1705a400cde89737ac898f45c6b65280f8c5
Author: Alberts Muktupāvels <alberts muktupavels gmail com>
Date:   Wed Apr 1 03:21:25 2020 +0300

    ci: add back extra coverity dependencies

 .gitlab-ci.yml | 4 ++++
 1 file changed, 4 insertions(+)
---
diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index adb6980..f163006 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -79,6 +79,10 @@ coverity:
   before_script:
     - apt-get update
     - *install-ubuntu-dependencies
+    - apt-get install -q -y --no-install-recommends
+                      ca-certificates
+                      clang
+                      curl
   script:
     - curl https://scan.coverity.com/download/linux64
       --data "token=$COVERITY_TOKEN&project=gnome-flashback"