Pass MR vars to downstream pipelines

This lets us fetch data from the MR that triggered a QA pipeline,
e.g., to get the changes from the MR and run only those tests.

scripts/trigger-build

@@ -91,7 +91,9 @@ module Trigger
         'TOP_UPSTREAM_SOURCE_PROJECT' => ENV['CI_PROJECT_PATH'],
         'TOP_UPSTREAM_SOURCE_JOB' => ENV['CI_JOB_URL'],
         'TOP_UPSTREAM_SOURCE_SHA' => ENV['CI_COMMIT_SHA'],
-        'TOP_UPSTREAM_SOURCE_REF' => ENV['CI_COMMIT_REF_NAME']
+        'TOP_UPSTREAM_SOURCE_REF' => ENV['CI_COMMIT_REF_NAME'],
+        'TOP_UPSTREAM_MERGE_REQUEST_PROJECT_ID' => ENV['CI_MERGE_REQUEST_PROJECT_ID'],
+        'TOP_UPSTREAM_MERGE_REQUEST_IID' => ENV['CI_MERGE_REQUEST_IID']
       }
     end