gitlab-ci: Build decorations in minimal CI run

A lot of integration tests rely on the fact that there is a
window decoration.

The `KWIN_BUILD_DECORATIONS` pretty much only disables
build of Aurorae window decoration plug-in but otherwise
has no impact on KWin's core code base in terms of ifdefs
or dependencies required.

Re-enable building decorations to unbreak those tests.

Signed-off-by: Victoria Fischer <victoria.fischer@mbition.io>

.gitlab-ci.yml

@@ -7,4 +7,4 @@ include:
 
 suse_tumbleweed_qt515_reduced_featureset:
     extends: suse_tumbleweed_qt515
-    script: python3 -u ci-utilities/run-ci-build.py --project $CI_PROJECT_NAME --branch $CI_COMMIT_REF_NAME --platform Linux --extra-cmake-args="-DKWIN_BUILD_DECORATIONS=OFF -DKWIN_BUILD_KCMS=OFF -DKWIN_BUILD_SCREENLOCKER=OFF -DKWIN_BUILD_TABBOX=OFF -DKWIN_BUILD_ACTIVITIES=OFF -DKWIN_BUILD_RUNNERS=OFF -DKWIN_BUILD_NOTIFICATIONS=OFF" --skip-publishing
+    script: python3 -u ci-utilities/run-ci-build.py --project $CI_PROJECT_NAME --branch $CI_COMMIT_REF_NAME --platform Linux --extra-cmake-args="-DKWIN_BUILD_KCMS=OFF -DKWIN_BUILD_SCREENLOCKER=OFF -DKWIN_BUILD_TABBOX=OFF -DKWIN_BUILD_ACTIVITIES=OFF -DKWIN_BUILD_RUNNERS=OFF -DKWIN_BUILD_NOTIFICATIONS=OFF" --skip-publishing