add custom chess engine

native/chess_engine/CMakeLists.txt

@@ -0,0 +1,42 @@
+cmake_minimum_required(VERSION 3.20)
+project(chess_engine LANGUAGES CXX)
+
+set(CMAKE_CXX_STANDARD 17)
+set(CMAKE_CXX_STANDARD_REQUIRED ON)
+set(CMAKE_CXX_EXTENSIONS OFF)
+
+# Shared library: chess_engine.dll (Windows) / libchess_engine.so (Linux).
+add_library(chess_engine SHARED
+    src/chess_engine.cpp
+    src/bitboard.cpp
+    src/zobrist.cpp
+    src/position.cpp
+    src/movegen.cpp
+    src/uci.cpp
+    src/perft.cpp)
+target_include_directories(chess_engine PUBLIC include)
+target_compile_definitions(chess_engine PRIVATE CHESS_ENGINE_BUILD)
+
+set_target_properties(chess_engine PROPERTIES
+    OUTPUT_NAME chess_engine
+    POSITION_INDEPENDENT_CODE ON)        # -fPIC on Linux (required for .so)
+
+# Export only the symbols marked with the CHESS_API macro.
+set(CMAKE_CXX_VISIBILITY_PRESET hidden)
+set(CMAKE_VISIBILITY_INLINES_HIDDEN ON)
+
+if (MSVC)
+    target_compile_options(chess_engine PRIVATE
+        $<$<CONFIG:Release>:/O2 /GL /DNDEBUG /arch:AVX2>
+        $<$<CONFIG:Debug>:/Od /Zi>)          # /Zi => .pdb for mixed-mode debugging
+    target_link_options(chess_engine PRIVATE
+        $<$<CONFIG:Release>:/LTCG>
+        $<$<CONFIG:Debug>:/DEBUG>)
+else()
+    # Portable server baseline. Do NOT use -march=native: the build host may have
+    # instructions the server lacks (SIGILL at runtime). Bump only once the server
+    # CPU floor is confirmed.
+    target_compile_options(chess_engine PRIVATE
+        $<$<CONFIG:Release>:-O3 -flto -DNDEBUG -march=x86-64-v2>
+        $<$<CONFIG:Debug>:-O0 -g>)
+endif()