list targets across multiple makefiles and create a meta dependency graph

[Martin d'Anjou]

Hi,

Is there a tool that creates a makefile out of multiple makefiles 
scattered in multiple sub directories and rebuilds a single dependency 
graph for the whole project?

I am toying with -p, -n and -d options to see how this could be done, but 
it looks like a lot of work. I am also looking at the perl module 
Makefile::parser, but I don't know yet how to best use it for this 
purpose.

Thanks,
Martin