[configs/releng] Add an empty machine-id

This makes systemd generate a machine-id on early boot and prevents it from thinking we need any "first boot" setup. We really don't want systemd thinking that, since we carefully prepared our root file system.

This also ensures every live environment has a unique machine id.
[configs/alter] Add an empty machine-id

See: 4a64f9b9d7527ce307b4678ad0fb76d2aad9002c
Also: https://mailman.archlinux.org/pipermail/arch-releng/2014-September/003435.html
prepare release
[configs/alter] install.txt: avoid redirection
[configs/alter] Toggle on numlock even in single user mode