Error building on cmake 4.1.2 (outdated zstd used by ccache)

[Andrej730]

Error:

CMake Error at /Users/m1/pyodide_env/pyodide/emsdk/emsdk/ccache/git-emscripten_64bit/build_emscripten_64/zstd-1.4.8/build/cmake/CMakeLists.txt:10 (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.

Apparently because buid is using https://github.com/juj/ccache which is still relying on zstd 1.4.8 and downloading it from the internet.

https://github.com/juj/ccache/blob/c4284c78e9ff286ee5208f449af4c2aaba062d37/cmake/Findzstd.cmake#L9

zstd 1.4.8:
https://github.com/facebook/zstd/blob/v1.4.8/build/cmake/CMakeLists.txt#L10

The first zstd version that has cmake 3.5+ is 1.5.6:
https://github.com/facebook/zstd/blob/v1.5.6/build/cmake/CMakeLists.txt#L10

[sbc100]

I'm not sure how much maintenance or usage https://github.com/juj/ccache has right now.

@juj should we keep maintaining it?