Allow bypassing `block device` checks

[eadwu]

For zfs as root, getting

lsblk: none: not a block device

[eadwu]

Or a subcommand that doesn't need any of those assumptions - pretty much installing the container to root and disregarding boot loader.

[cgwalters]

Hi, can you elaborate a bit more with

• exactly what command you're running
• your intended use case

[eadwu]

What I am running right now is

bootc install to-filesystem --skip-fetch-check --root-mount-spec=UUID=3d09d690-6110-3c87-abb6-c286e58cf8ae --boot-mount-spec=UUID=3d09d690-6110-3c87-abb6-c286e58cf8ae --karg=root=UUID=3d09d690-6110-3c87-abb6-c286e58cf8ae --source-imgref oci-archive:/oci/bootc.oci /fakeroot

UUIDs are fake and I can modify the kernel arguments for them later on so I don't really mind that part.

/fakeroot is a bind-mounted directory from the host under the zfs dataset rpool/subvolume/bootc

Running the above command returns an error

Installing image: docker:///oci/bootc.oci
ERROR Installing to filesystem: Subprocess failed: ExitStatus(unix_wait_status(8192))
lsblk: rpool/subvolume/bootc: not a block device

Usecase is to use bootc with zfs as the filesystem. From what I can see in the code, it is used for a partition table check and then for the bootloader (more essential for the zipd function).

[eadwu]

The problem areas I've isolated for my usecase

eadwu@c556c8e (unsuitable commit for merging though resolves the issues)