[CMake] SUBDIRS PREORDER semantics with ADD_DEPENDENCIES ?

[Eric BOIX]

	Dear Brad King,

Quoting Brad King <brad.king at kitware.com>:
> Just create one target in the subdirectory:
> [...]
> ADD_CUSTOM_TARGET(build_figs ALL DEPENDS ${ALL_OUT})
> 
> Then in the top level directory:
> [...]
> ADD_DEPENDENCIES(build_docs build_figs)

Perfect semantics (for what I meant), trivial to do, elegant, and it does
work perfectly...

	Thanks a lot !
	Eric Boix, a happy cmake user...