Add CMake option to change target distro at compile time

[otreblan]

I was thinking of adding an option to activate a source file depending of the distro. Like (at configure time): cmake -DPALEOFETCH_DISTRO=ubuntu .. or cmake -DPALEOFETCH_DISTRO=arch-linux ..

#5

[Titaniumtown]

Wouldn't it just be more efficient to do it in the program?

[otreblan]

This is done at configure time

[Titaniumtown]

just saw @sam-barr's comment on #59 about that