Modernize Build System: Migrate from setup.py to CMake + scikit-build-core (#126)

[BoPeng]

Summary

This PR modernizes the simuPOP build system by migrating from the legacy setup.py distutils-based build to a modern CMake + scikit-build-core system. This provides better cross-platform support, automatic compiler feature detection, and compatibility with modern Python packaging standards (PEP 517/518).

Changes

New Files

• CMakeLists.txt: Complete CMake build configuration

  • Automatic detection of compiler features (isfinite, isnan, isinf, etc.)
  • Automatic Boost download if not present
  • Builds all 10 module variants (std, op, la, laop, ba, baop, mu, muop, lin, linop)
  • OpenMP support detection
  • Uses pre-generated SWIG wrapper files to avoid SWIG version compatibility issues

• cmake/SimuPOPConfig.h.in: Template for auto-generated config header

  • Replaces manual platform detection in config.h
  • Uses CMake's check_function_exists() and check_symbol_exists() for portable feature detection

• pyproject.toml: Modern Python packaging configuration

  • Uses scikit-build-core as build backend
  • Dynamic version from src/_version.py
  • Proper metadata and classifiers

Modified Files

• src/simuPOP_cfg.h: Updated to use auto-generated config header from CMake build
• src/_version.py: Bumped version to 1.1.18

Build Instructions

# Using pip (recommended)
pip install .

# Or using python -m build
pip install build
python -m build

# Direct CMake build (for development)
cmake -B build -S .
cmake --build build -j4

Key Features

1. Platform-independent feature detection: No more manual #ifdef blocks for different platforms
2. Modern Python packaging: Compatible with pip, build, and other PEP 517 tools
3. Pre-generated SWIG wrappers: Avoids SWIG version compatibility issues
4. Automatic Boost handling: Downloads Boost if not present
5. Single source of truth for version: src/_version.py feeds both CMake and pyproject.toml

Compatibility

• Python 3.9+
• CMake 3.20+
• C++17 compatible compiler
• macOS, Linux, Windows (with Visual Studio 2022)