[libhandy/wip/exalm/ci] ci: Specify the image for api-visibility job

[Alexander Mikhaylenko <alexm src gnome org>]

commit ee2702ed669c75470ecf79c6b02be0bf4d13dfb5
Author: Alexander Mikhaylenko <alexm gnome org>
Date:   Fri May 22 15:06:40 2020 +0500

    ci: Specify the image for api-visibility job

 .gitlab-ci.yml | 1 +
 1 file changed, 1 insertion(+)
---
diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index 1c3cbc09..a5f78979 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -24,6 +24,7 @@ before_script:
     ninja -C _build
 
 api-visibility:
+  image: debian:buster
   <<: *tags
   stage: build
   script: