iOS only runs app bundles, so with HEADLESS=ON the iOS build makes
PPSSPPHeadless an app (org.ppsspp.headless) that starts UIKit and runs
the headless main on a thread with the arguments devicectl launched it
with. Vulkan only, and the IR interpreter since there's no JIT.
frametests.py --ios installs it, copies over the dumps the device lacks,
and compares each render with the host's Vulkan one like --adb does.
Each devicectl call costs a second or two, so the new --screenshot-dir
lets one launch render a batch of dumps.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>