[glibmm] CI: Accept warnings from clang++

[Kjell Ahlstedt <kjellahl src gnome org>]

commit 1cca23fa4ff3992944792a27ad0a4ccae2e494fa
Author: Kjell Ahlstedt <kjellahlstedt gmail com>
Date:   Wed May 4 17:02:38 2022 +0200

    CI: Accept warnings from clang++

 .gitlab-ci.yml | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/.gitlab-ci.yml b/.gitlab-ci.yml
index b21654b5..c84ff199 100644
--- a/.gitlab-ci.yml
+++ b/.gitlab-ci.yml
@@ -158,7 +158,7 @@ release_clang_build:
     - cp -r installdir/usr /
     - mkdir _build && cd _build
     # -Ddebug=false + -Doptimization=3 correspond to -Dbuildtype=release
-    - CC=clang CXX=clang++ meson --prefix=/usr --libdir=lib -Ddebug=false -Doptimization=3 -Dwarnings=fatal
+    - CC=clang CXX=clang++ meson --prefix=/usr --libdir=lib -Ddebug=false -Doptimization=3 -Dwarnings=max
     - meson compile
     - 'meson test --suite glibmm:'
     - meson install