macOS actions with Cmake 4 can't build libelfin

[silvigon]

Github actions that compile Ripes on macOS (both tests and release jobs) aren't able to build libelfin, causing the job to fail:

CMake Error at _deps/libelfin-src/CMakeLists.txt:1 (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.

This error may be caused by the new macOS 26 runner that was introduced a couple days ago, as this occurs on my fork with both my own branches, as well as the copy of master that I keep for reference, so there isn't any code difference to point to that would cause this.

[silvigon]

On further inspection, the update to Cmake 4 is probably the actual culprit; the macOS 26 runner isn't in general availability yet.