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

See https://github.com/alpinelinux/aports/pull/3886

"$@" works differently on ash and dash. `foo="$@"` assigns only the
first item (according to IFS) to the variable on dash.