CI: building zlib fails

[agarny]

Before we can build our JavaScript bindings, we first need to build zlib (every time!?), but its CMakeLists.txt file uses 3.0 for CMAKE_MINIMUM_REQUIRED while it should, nowadays, be 3.5 minimum (see https://github.com/cellml/libcellml/actions/runs/15032981800/job/42249275970):

configure: cmake -G Ninja -S zlib -B zlib-wasm -DCMAKE_BUILD_TYPE=Release '-DCMAKE_INSTALL_PREFIX=~/wasm' -DBUILD_SHARED_LIBS=OFF -DCMAKE_TOOLCHAIN_FILE=/opt/homebrew/Cellar/emscripten/4.0.8/libexec/cmake/Modules/Platform/Emscripten.cmake -DCMAKE_CROSSCOMPILING_EMULATOR=/opt/homebrew/opt/node/bin/node
CMake Error at CMakeLists.txt:38 (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!
emcmake: error: 'cmake -G Ninja -S zlib -B zlib-wasm -DCMAKE_BUILD_TYPE=Release '-DCMAKE_INSTALL_PREFIX=~/wasm' -DBUILD_SHARED_LIBS=OFF -DCMAKE_TOOLCHAIN_FILE=/opt/homebrew/Cellar/emscripten/4.0.8/libexec/cmake/Modules/Platform/Emscripten.cmake -DCMAKE_CROSSCOMPILING_EMULATOR=/opt/homebrew/opt/node/bin/node' failed (returned 1)

[agarny]

From what I can see, the same applies to libxml2.