gitlab CI: add a -Werror job (allowed to fail)

Most of the time we don't pay attention to the details in the actual
jobs, them passing is good enough. So let's have at least one job with
-Werror that fails if our CI has warnings we don't have locally.
Allowed to fail because we don't want to be beholden to compiler changes
(though having this fail for a long period makes the job less useful
again).

Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>

.gitlab-ci.yml

@@ -256,6 +256,13 @@ valgrind@fedora:35:
   before_script:
     - dnf install -y valgrind
 
+werror@fedora:35:
+  extends:
+    - .fedora-build@template
+  variables:
+    MESON_ARGS: '-Dwerror=true'
+  allow_failure: true
+
 
 #################################################################
 #                                                               #

.gitlab-ci/ci.template

@@ -277,6 +277,13 @@ valgrind@{{distro.name}}:{{version}}:
   before_script:
     - dnf install -y valgrind
 
+werror@{{distro.name}}:{{version}}:
+  extends:
+    - .{{distro.name}}-build@template
+  variables:
+    MESON_ARGS: '-Dwerror=true'
+  allow_failure: true
+
 {% endfor %}
 
 #################################################################