[gimp/wip/Jehan/fix-clang-CI] gitlab-ci: fix recently broken CLang compilation.

[Jehan <jehanp src gnome org>]

commit b0fea236fe4752fe24d4b6314d7ec80abeb58107
Author: Jehan <jehan girinstud io>
Date:   Sun Mar 15 22:21:19 2020 +0100

    gitlab-ci: fix recently broken CLang compilation.
    
    Fixes:
    > /usr/bin/ld: cannot find -lomp

 .gitlab-ci.yml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index c33030cdb4..da8c0a0294 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -157,7 +157,7 @@ gimp-debian/testing-clang:
     CXX: "clang++"
   script:
     - apt-get install -y --no-install-recommends
-        clang
+        clang libomp
     - meson _build
       --prefix="${INSTALL_PREFIX}"
       -Dpython=always