Stage the runtime-host assets here before building (see ../../../../README.md):
proot static aarch64 proot binary
rootfs.tar glibc Ubuntu rootfs (minimal base for the smoke test; later the
full base with runtime libs + the pgh bundle baked in)
Extraction uses the platform /system/bin/toybox, so no tar binary is bundled.
The project compiles without these; PghNodeService fails at runtime if they are
missing. They are .gitignored (too large + machine-built).