$sysli is local to setup_syslinux()
util-linux has mountpoint(1), is_mounted gone

no need to awk /proc/mounts
chrooted() gone, ROI was too low
efibootmgr(8) call uses long options

readability for a lesser-known interface.
two-stage operation: anarchinst generates a script

instead of charging ahead with the installation right away,
anarchinst now generates syslinux.cfg and doit.zsh, the latter
is a simple linear script doing the actual installation.

this makes it easier to test, verify and tweak the install
procedure.