Fix wasm build.

[trivialfis]

Nice to have. However, let's not include it in the support matrix.

[Copilot]

Pull Request Overview

This PR fixes the WebAssembly (WASM) build by addressing compatibility issues with the Emscripten toolchain. The changes focus on resolving type conversion issues and disabling thread-related dependencies that are not supported in WASM environments.

• Explicit type annotations to resolve implicit conversions that fail in WASM builds
• Conditional compilation to exclude threading support for Emscripten builds
• CMake configuration updates to handle WASM-specific requirements

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

File	Description
src/common/threading_utils.h	Adds explicit type annotation for block_beg variable
src/c_api/c_api.cc	Refactors buffer creation with explicit type aliases and casts
cmake/Utils.cmake	Conditionally excludes thread linking for Emscripten builds
CMakeLists.txt	Conditionally excludes thread package finding for Emscripten builds

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