Cross-build game products for macOS from a Linux host with osxcross,
next to the existing Linux-to-Windows MinGW toolchain file.
- PSX_DARWIN_ARCH selects x86_64 (default) or arm64.
- OSXCROSS_ROOT points at the osxcross target directory. It falls back to
$OSXCROSS_ROOT, then to the osxcross-conf on PATH.
- CMAKE_OSX_DEPLOYMENT_TARGET defaults to 11.0.
- ld64 is named with --ld-path, so the build does not depend on
osxcross/bin being on PATH.
- The host's pkg-config files are hidden from the Darwin build.
Documented in docs/BUILDING.md and docs/ci/README.md.