Add Linux build script for TensorSharp.GGML.Native and make CMake Apple-specific settings conditional

[zhongkaifu]

Motivation

• Provide an easy way to build the native GGML bridge on Linux as a CPU-only shared library.
• Ensure the CMake configuration does not require Apple-only languages or Metal when building on Linux.

Description

• Add TensorSharp.GGML.Native/build-linux.sh, a helper script that configures a Release build directory and builds the GgmlOps target with cmake and cmake --build.
• Update TensorSharp.GGML.Native/CMakeLists.txt to conditionally enable Objective-C/Objective-C++ and Metal settings only when APPLE is detected, and disable Metal on non-Apple platforms.
• Document the Linux build steps in README.md and readme_cn.md, showing cd TensorSharp.GGML.Native and bash build-linux.sh and noting the output libGgmlOps.so.

Testing

• Ran bash TensorSharp.GGML.Native/build-linux.sh on Linux, which completed successfully and produced libGgmlOps.so.
• The CMake configure and build steps executed without errors (cmake -S ... -B ... -DCMAKE_BUILD_TYPE=Release and cmake --build ... --target GgmlOps).

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Codex Task