[gimp/wip/Jehan/distcheck] gitlab-ci: just test if a make distcheck would work.

[Jehan <jehanp src gnome org>]

commit e19b45496aec6415261bf74dc163ff6be260e6b4
Author: Jehan <jehan girinstud io>
Date:   Sun Apr 19 00:32:46 2020 +0200

    gitlab-ci: just test if a make distcheck would work.

 .gitlab-ci.yml | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)
---
diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index 78c0286c76..f6f9f37d3e 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -140,8 +140,9 @@ gimp-debian/testing-autotools:
         --with-python=force
         --with-javascript=force
         --with-lua=force
+        --enable-gtk-doc
     - make -j "$(nproc)"
-    - make check
+    - make distcheck
 
 gimp-debian/testing-meson:
   extends: .gimp-debian/testing-base