Same fix as cd4302c for intelcpu: the bare sed against /etc/default/grub
missed systemd-boot and already-generated GRUB+BLS boot entries. Update
every kernel-argument surface idempotently, guarded by file existence:
/etc/kernel/cmdline, /etc/default/grub, and the options line of every
/boot/loader/entries/*.conf. Guard the nested=1 append as well.