.gitlab-ci.yml: test changed pipelines

Changes to the pipeline definition file should trigger the same set of
builds as changes to the shared jobs.

Signed-off-by: Zygmunt Krynicki <zygmunt.krynicki@huawei.com>

.gitlab-ci.yml

@@ -71,6 +71,7 @@ aggregate-docs:
         - flavours/**/*
         - meta-*/**/*
         - .oniro-ci/*
+        - .gitlab-ci.yml
       # When building a merge request substitute the CI_ONIRO_MANIFEST_URL to point
       # to the incoming repository, and CI_ONIRO_MANIFEST_BRANCH, to the right
       # branch name. This allows testing the changes coming into project. This