Add QEMU user-mode emulation for building aarch64 images (uConsole CM5):
- qemu-user-static: Static QEMU binaries for user-mode emulation
- binfmt-support: Linux kernel support for recognizing binary formats
- qemu-user-binfmt: Registers QEMU handlers with binfmt_misc
Enables cross-compilation of NixOS configurations for ARM devices
from the x86_64 Hermes container.
Depends on PR #7, #8, and #9
