build fails with cmake version >= 4

[nicolaslg]

At least one of the dependencies, double-conversion-3.3.0 for example, fails during configuration because support for cmake policies < 3.5 was dropped in cmake >= 4.

For the time being to avoid this problem we should use a version of cmake < 4.

Note that the latest cmake version included in the snap store is currently 4.0.3, so one should downgrade the snap installed version and modify the .spack/packages.yaml configuration file to select an appropriate cmake.