[Bug] Windows build fails with Clang/MSVC due to missing #include <chrono>

Summary

Building on Windows with ClangCL fails due to missing #include header and const pointer type mismatch in bitnet-mad.cpp.

Steps to Reproduce

1. Clone the repository on Windows 11
2. Install Clang 19 via Visual Studio 2022 Build Tools + clang-cl
3. Run CMake configuration and build
4. Observe compilation errors

Expected Behavior

Code should compile on Windows with ClangCL without errors

Actual Behavior

Two compilation errors occur:

Error 1: Missing #include

The following files use std::chrono without explicitly including :

• 3rdparty/llama.cpp/common/common.cpp
• 3rdparty/llama.cpp/common/log.cpp
• 3rdparty/llama.cpp/examples/imatrix/imatrix.cpp
• 3rdparty/llama.cpp/examples/perplexity/perplexity.cpp

On Linux/GCC, is pulled in implicitly, but Clang on Windows is stricter.

Error 2: Const pointer mismatch (src/ggml-bitnet-mad.cpp line 811)

error: cannot initialize a variable of type 'int8_t *' with an rvalue of type 'const int8_t *'

Root Cause Analysis

The root cause is platform-specific header dependency and type constness:

1. Header Issue: GCC on Linux transitively includes through other headers, but Clang/MSVC on Windows does not
2. Type Issue: The code at line 811 declares int8_t * but receives a const int8_t *, which should be const int8_t *

Proposed Solution

1. Add #include <chrono> to the four affected files
2. Change line 811 from int8_t * to const int8_t *

Environment

• OS: Windows 11
• Compiler: Clang 19 (via Visual Studio 2022 Build Tools + clang-cl)
• CMake: 3.x

Start with the four listed files under 3rdparty/llama.cpp/common and examples, then inspect src/ggml-bitnet-mad.cpp around line 811. Reproduce the CMake build with clang-cl on Windows and verify that the missing chrono headers and const pointer error are resolved without introducing other compiler errors.