Adds an arm64 simulator platform to the iOS toolchain. The simulator build
renders with Metal only: it doesn't link MoltenVK, and loads Vulkan at
runtime like the libretro core, so Vulkan reports itself unavailable and
the config falls back to Metal.
b-ios-simulator.sh builds the App Store variant and runs it on the booted
simulator, or on one of a given device type, for App Store screenshots of
devices we don't have.
Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>
