[CMake] CMake rebuilds every time

[Arindam Mukherjee]

Hi,

I have a cross-platform build setup using cmake 2.8.9 which builds on
5 different OSs. However it rebuilds every time even when neither the
Makefile timestamps nor the source file timastamps had changed.
Examining the generated Makefiles I can see that all .o, .i and .s
targets have been marked .PHONY. Don't know if this is the reason for
it. How to fix this to not rebuild every time but do incremental
builds?

Thanks,
Arindam