Created attachment 163074 [details]
Patch for calling ant target on parent project(s) for CosAction.
Current behaviour is that changed project is rebuilt, all dependent projects (transitive) are rebuilt sequentially. Can be changes as you want.
Please try and comment.
The requirement to have project open in the UI is so non-NetBeans like. Thus I implemented https://github.com/graalvm/mx/commit/c7c4617024305d36cbb2db61a9ae9a761c8342d7 - hopefully it means we don't need this "UI only dependency check".