[CMake] compiling implementation first in dependancies

[Philippe Fremy]

Alexander Neundorf wrote:
>> If I change z.h and z.cpp to add a new method, I usually don't get z.h
>> to work out of the box, but only realize it when compiling z.cpp .
>> What's annoying is that cmake will first compile a.cpp , b.cpp , c.cpp
>> and then only z.cpp .
> 
> Try "make help" to get a list of all targets, there should be also one for the 
> object file.
> 

Oh, I was not aware of that cool make help.

Thanks Alex.

	Philippe