[Cmake] dependencies

[Franck Bettinger]

Hi,

I tried to add a dependency that was not automatically generated by cmake in 
a CMakeList.txt using the command:

ADD_DEPENDENCIES(drawingimpl.cxx 
${allvxl_SOURCE_DIR}/obj/programs/drawing/drawing.h)

Apparently it doesn't change anything in the generated Makefile (at least on 
linux). Anyone has any idea why it does this, or how can I add a user defined 
dependency ?

Cheers,
Franck