Base Class Project with Multiple Concrete Sub Projects Manifest Query?

I have a project which uses multiple project files.  A virtual base class project with multiple concrete projects which make use of the base class.  I get the following compiler warning when building the projects.

"A valid 'project.manifest' property was not defined within a jungle file."

The project compiles and all is well with the binary image.

Which relates to the fact I have no project manifest declared in the Base Class project Jungle file.  However if I declare a Project Manifest with

project.manifest = manifest.xml
in the Base Class Jungle file I get a compiler error and abort with

"Attempting to reset project property 'manifest'." as I also have a jungle file in the sub projects, and this is where I need them.

Any tips on what do I need to do to plicate the compiler so I do not get any warnings or errors?