CI multi-project pipeline

I am trying to setup a complex multi-project pipeline, something line:

Project A  -> Project B
           -> Project C -> Project E
           -> Project D -> Project E

I was able to setup all the .gitlab-ci.yml to trigger the tree correctly and update the top level status based on failure on the dependencies. What I am now trying to do is getting Project E job to only be executed once. Is there a way to get it to dedupe and get it to run that job once?