Add compatibility with CMake 4.0

[lcrh]

Brew install on a new mac fails due to cmake incompatibility.

% brew install SRI-CSL/sri-csl/libpoly

==> Auto-updating Homebrew...
Adjust how often this is run with HOMEBREW_AUTO_UPDATE_SECS or disable with
HOMEBREW_NO_AUTO_UPDATE. Hide these hints with HOMEBREW_NO_ENV_HINTS (see `man brew`).
==> Tapping sri-csl/sri-csl
Cloning into '/opt/homebrew/Library/Taps/sri-csl/homebrew-sri-csl'...
remote: Enumerating objects: 303, done.
remote: Counting objects: 100% (24/24), done.
remote: Compressing objects: 100% (24/24), done.
remote: Total 303 (delta 4), reused 2 (delta 0), pack-reused 279 (from 1)
Receiving objects: 100% (303/303), 44.87 KiB | 918.00 KiB/s, done.
Resolving deltas: 100% (117/117), done.
Tapped 3 formulae (15 files, 61.0KB).
==> Fetching sri-csl/sri-csl/libpoly
==> Downloading https://github.com/SRI-CSL/libpoly/archive/v0.1.13.tar.gz
==> Downloading from https://codeload.github.com/SRI-CSL/libpoly/tar.gz/refs/tags/v0.1.13
#-#O=- #      #
==> Installing libpoly from sri-csl/sri-csl
==> cmake .. -DLIBPOLY_BUILD_PYTHON_API=OFF -DLIBPOLY_BUILD_STATIC=OFF -DLIBPOLY_BUILD_STATIC_PIC=OFF
Last 15 lines from /Users/leo/Library/Logs/Homebrew/libpoly/01.cmake:
-DLIBPOLY_BUILD_STATIC_PIC=OFF
-DCMAKE_BUILD_TYPE=Release
-DCMAKE_INSTALL_PREFIX=/opt/homebrew/Cellar/libpoly/0.1.13

CMake Error at 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.


-- Configuring incomplete, errors occurred!

If reporting this issue please do so at (not Homebrew/* repositories):
  https://github.com/sri-csl/homebrew-sri-csl/issues

leo@mac ~/cvc5 % cmake --version
cmake version 4.0.0