systemd-gpt-auto-generator fails in the live environment

For some while now, when booting the ISO, you can observe a message that systemd-gpt-auto-generator has failed:

[   10.489449] systemd[184]: /usr/lib/systemd/system-generators/systemd-gpt-auto-generator failed with exit status 1.

journal shows a little more details:

systemd-gpt-auto-generator[197]: Reading EFI variable /sys/firmware/efi/efivars/LoaderDevicePartUUID-4a67b082-0a4c-41cf-b6c7-440b29bb8c4f.
systemd-gpt-auto-generator[197]: open("/sys/firmware/efi/efivars/LoaderDevicePartUUID-4a67b082-0a4c-41cf-b6c7-440b29bb8c4f") failed: No such file or directory
systemd-gpt-auto-generator[197]: EFI loader partition unknown, exiting.
systemd-gpt-auto-generator[197]: (The boot loader did not set EFI variable LoaderDevicePartUUID.)
systemd-gpt-auto-generator[197]: Failed to open device: No such device

systemd-boot didn't/couldn't set LoaderDevicePartUUID. Most likely because of the GPT partition type UUID for the partition in the invalid GPT (we're setting the correct type ID in MBR).

Since we do not want any GPT partition automounting in the live environment, it may be best to disable systemd-gpt-auto-generator.

This can be done in two ways:

1. By adding systemd.gpt_auto=no to kernel parameters in configs/{baseline,releng}/efiboot/loader/entries/*.conf. See systemd-gpt-auto-generator(8).
2. By symlinking configs/{baseline,releng}/airootfs/etc/systemd/system-generators/systemd-gpt-auto-generator to /dev/null. See systemd.generator(7).

Since I don't like needlessly polluting the kernel command line, I'd prefer the second option.