[CMake] Per-target compiler flags?

[Remi Denis-Courmont]

   Hello,

I am trying to port a project to CMake, but I couldn't find anyway to specify
C preprocessor defines on a per-target (or alternatively, per-source) basis.
The project is compiling the same source files multiple times with different
defines, resulting in different object code... But it seems like
ADD_DEFINITIONS won't support this case.

Any solution?

-- 
Remi Denis-Courmont
http://www.simphalempin.com/home/