cmake/Ccache.cmake: raise cmake_minimum_required() as newer CMake versions warn that support for CMake < 3.5 is going to be dropped at some later point

[rouault]

No description provided.

[kbevers]

Will this make CMake 3.9 a requirement? If so, RFC3 states that

Changes for software package dependencies can be introduced with minor version releases of PROJ. Changing the version requirements for a dependency needs to be approved by the PSC.

[rouault]

Will this make CMake 3.9 a requirement?

it is already :-) :-) Cf root CMakeLists.txt: /~https://github.com/OSGeo/PROJ/blob/master/CMakeLists.txt#L12

[kbevers]

it is already :-)

Well, great :-) I guess RFC3 is not up to date then. It says the minimum CMake requirement is 3.5

[rouault]

I guess RFC3 is not up to date then

was overriden by a PSC vote in Feb 2020: https://lists.osgeo.org/pipermail/proj/2020-February/009324.html

[kbevers]

Yes, that was clear from the previous message. My point was that it would be nice to have the current requirements reflected in the RFC - I don't regard them as static documents

[mwtoews]

It could also be removed (e.g. this was done for geos libgeos/geos@3d4870f). This statement is only needed per-project, whereas I might have thought this was a per-module spec. But this merge fix is also fine.