Minimum required cmake version

[Michael Pyne]

On Sat, Dec 31, 2016 at 03:47:00PM +0100, Sven Brauch wrote:
> Hey,
> 
> On 27/12/16 19:30, Aleix Pol wrote:
> > +1 on changing to 3.0.
> Thanks for your opinion on the matter. I also think we should just bump
> it, 3.0 is old enough -- as said it's even easily available on CentOS 6.
> 
> Question is, should I change it on _all_ frameworks or just those using
> Q_GADGET (i.e. those which actually need cmake 3)?

If we change the CMake requirement for one framework it should be
changed for them all.  They are tested, released, and supported as a
unit even though they have separate tiers and could theoretically be put
together in a piecemeal fashion.

There might also be an easy way to change it in extra-cmake-modules but
I think some of the buildsystem devs would know more about that.

Regards,
 - Michael Pyne