best way to structure project with an "empty" dir

[John Richetta]

I have a project that has a directory structure like this:

                  TopDir
                    |
            +----------------+----+
            |                |    |
          AppDir           other dirs...
          |    |
          A    B

The top level of this project is where one invokes configure and  
make.  However, the project has traditionally been structured such  
that the final executable resides in subdirectories of AppDir, and  
the actual source code primarily resides in subdirs of AppDir.

While the best answer is probably to reorganize this structure, let's  
say that time does not really permit this (nor is the client  
particularly keen to reorganize this project).

So, presently, I have a Makefile(.am) in AppDir that builds the  
application from subdirectory sources, and links the final  
executable, leaving it in AppDir.  The Makefile(.am) in TopDir does  
almost nothing, besides invoke submakes.  This is closest to how  
things have worked in the past.

The problem with how this is working given how I've set this up is  
that the top makefile generates an error, as I'm having it build a  
dummy application, with no source files.  This isn't fatal, but I'd  
still really like to eliminate this error (without introducing dummy  
application source to be built).

I'm not sure how to achieve this: I've been over the documentation  
many times, and I'm pretty sure there is an example showing  
indirectly how to do this, but I'm having trouble finding it.

A pointer to it, or some advice about how to achieve this (ie., no  
built binary, but all submakes invoked), or some similar result,  
would be much appreciated.

Thanks, -jar