don't assume `unzip` is a thing

[rcgoodfellow]

Taking voxel for a spin on a bench sled hits this issue.

2593R21G # pfexec ./voxel image create \
>   --from-tuf tuf-b40e1db26-ci.zip \
>   --sled-agent osa-b40e1db26.tar.gz \
>   --dataset fpool/falcon
Error: run unzip -Z1

Caused by:
    No such file or directory (os error 2)

There are good rust crates for decompressing many file formats, falcon leverages them to do decompression natively for the compressed files it consumes.