[gimp] gitlab-ci: run distcheck with multi-jobs.

[Jehan <jehanp src gnome org>]

commit 63dddb5eb70eebdeede54e75d3037922ab935483
Author: Jehan <jehan girinstud io>
Date:   Fri Aug 7 15:30:05 2020 +0200

    gitlab-ci: run distcheck with multi-jobs.

 .gitlab-ci.yml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index 5102e39741..3d3ca3ef49 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -157,7 +157,7 @@ gimp-distcheck-debian:
         --with-lua=force
         --enable-gtk-doc
     - make -j "$(nproc)"
-    - make distcheck
+    - make -j "$(nproc)" distcheck
   allow_failure: true
 
 gimp-meson-debian: