fix for windows machines using out of source builds (CMake)

No you can use it with:
--object-directory=build_path
--root=source_path

I have also tested some other situations it worked fine for me - so maybe it also works fine for others :-)
I am not able to test i on linux or mac - so if someone can test it would be great.

I am also not sure if I change the code in that way the authors idea was. Because in the help I read that the objdir is used to search for the covarage but when you use this objdir it doesn´t do that. So for me this was an error and so I changed this behavior - no it matches with the documentation.

PS.:
For jenkins cobertura users => if you use root an objdir the source lookup also works fine :-)