ci: Do not werror on deprecations

This often blocks updating the base image of the CI since we
have to wait to port away from all the deprecated apis each time.

That's work that is done independantly usually and blocking image
updates, means that more regressions that would have got caught
by the newer toolchain sneak past and get merged.

Deprecations will still show up when developing locally.

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/5543>

.gitlab-ci.yml

@@ -40,6 +40,10 @@ variables:
   WINDOWS_IMAGE: "$CI_REGISTRY_IMAGE/$WINDOWS_AMD64_SUFFIX:$WINDOWS_TAG-$GST_UPSTREAM_BRANCH"
   WINDOWS_UPSTREAM_IMAGE: "$CI_REGISTRY/$FDO_UPSTREAM_REPO/$WINDOWS_AMD64_SUFFIX:$WINDOWS_TAG-$GST_UPSTREAM_BRANCH"
 
+  _BUILD_IGNORE_DEPRECATIONS: >
+    -Dc_args="-Wno-error=deprecated-declarations"
+    -Dcpp_args="-Wno-error=deprecated-declarations"
+
   DEFAULT_MESON_ARGS: >-
     -Dlibnice:tests=disabled
     -Dlibnice:examples=disabled
@@ -278,7 +282,7 @@ commitlint:
     fi
   - echo $ARGS
   - date -R
-  - meson setup build/ $(echo ${ARGS})
+  - meson setup build/ ${_BUILD_IGNORE_DEPRECATIONS} $(echo ${ARGS})
   - date -R
   - ninja -C build/
   - date -R