- Detect case-insensitive filesystems (macOS/Windows) and identify files
  that collide due to case differences (e.g. Default.html vs default.html)
- Skip conflicting files in verification and link creation instead of
  reporting false MISSING/SIZE MISMATCH errors
- Use python.org universal installer for Intel macOS build (fixes
  _mkfifoat symbol error on older macOS versions)
- Set MACOSX_DEPLOYMENT_TARGET=10.13 for both macOS builds
- Bump version to 2.4.1