[CMake] cpack -G DEB for subdirectories

[blinkeye]

> You may want to use custom CPack scripts for different purposes. By default,
> CPack uses script generated by CMake in top-level directory, but you can
> write your own one (and as many as you want) and pass it to cpack as command
> line parameter.
> Of course, install components could be great help in packaging.
> 

I take it you're talking about the '--config' option. That sounds like a
workaround if it's possible to use/include some globals to reduce the overhead.