Closes #21

Fixes #12

When using the --script-chroot option, chroot is called with just sh
(relative path), relying on the host environment's $PATH to find the
executable. At least on Arch Linux, this does not work, as Arch Linux
by default does not have /bin in the PATH (/bin is just a symlink to
/usr/bin).

Since the chroot system was just built and it is know to contain
/bin/sh, I think it makes sense to just call it explicitly here.

Related to https://github.com/alpinelinux/alpine-make-rootfs/issues/10



Co-Authored-By: Conrad Hoffmann <[email protected]>

Since Alpine 3.7.

Resolves #6

Co-Authored-By: Jakub Jirutka <[email protected]>
I just refactored the code.

See https://github.com/alpinelinux/apk-tools/commit/37fbafcd928c466c82c892a7868d686d710e5d07

Arch Linux does not have /bin or /sbin in PATH by default, so the script
fails to execute extlinux, update-extlinux, mkfs.* etc.

If I understand it correctly, the default propagation type is private,
but f**king systemd mounts everything as shared. This is especially
problematic when doing recursive bind, which is not our case, but still
better to explicitly set propagation to private anyway.

See: https://lwn.net/Articles/689856/, https://lwn.net/Articles/690679/

Resolves #3

Resolves #3