Add native aarch64 support

[cverna]

Problem

bcvk does not currently support running aarch64 container images on native aarch64 hardware.

EFI zboot kernels

Fedora aarch64 kernels (since F37+) are packaged as EFI zboot images—a PE-format wrapper around a zstd-compressed kernel payload. QEMU's -kernel flag cannot load these directly and fails with:

unable to handle EFI zboot image with 'zstd' compression

x86_64 kernels are shipped uncompressed, so this issue doesn't occur there.

Credential injection with direct kernel boot

On aarch64 with direct kernel boot (-kernel), SMBIOS-based credential injection doesn't work because there's no UEFI firmware to expose SMBIOS tables. This breaks SSH key injection.

Proposed Solution

• Detect EFI zboot images by parsing the PE/zboot header
• Decompress zstd-compressed payloads before passing to QEMU
• Implement virtiofs-based credential injection (aligned with systemd upstream proposal)

A working implementation is available at: https://github.com/cverna/bcvk/tree/aarch64-support

Related

• Issue [Feature request] Emulate other CPU architectures #258 (cross-architecture emulation - different use case)

[alicefr]

/cc

[cgwalters]

A working implementation is available at: https://github.com/cverna/bcvk/tree/aarch64-support

I commented there, can you do a PR for it?