Support cmake 4.0 without workarounds

[brawer]

When building libosmium 2.22.0 with cmake 4.0, configuration fails like this:

CMake Error at CMakeLists.txt:9 (cmake_minimum_required):
  Compatibility with CMake < 3.5 has been removed from CMake.
  Update the VERSION argument <min> value.  Or, use the <min>...<max> syntax
  to tell CMake that the project requires at least <min> but has been updated
  to work with policies introduced by <max> or earlier.
  Or, add -DCMAKE_POLICY_VERSION_MINIMUM=3.5 to try configuring anyway.
-- Configuring incomplete, errors occurred!
>>> ERROR: libosmium: build failed

See command line invocation and error log. As a workaround, users can pass -DCMAKE_POLICY_VERSION_MINIMUM=3.5, which we'll do for now when packaging libosmium for Alpine Linux. However, consider updating CMakeLists.txt, so people can build libosmium with modern CMake without trouble.

[joto]

There is a change in master, I hope this works for you. I don't have a CMake 4 to test with.

[LecrisUT]

Thank you for the assistance.

I would recommend to add a higher-bound there as well (usually it is the highest CMake version you have in the CI) in order to avoid future maitenance. CMake said that they will be dropping policies every 3 years, and that would avoid having to bother you again in the next round.

(PS: FATAL_ERROR keyword there is a no-op)