First, add the builtin udev rules to /etc/udev/rules.d so they are used.
Then, add all networkd .link units to the initrd. This is done in the
old stage 1 as well so I assume this is needed even when networkd is not
used. I assume this is for things like changing the MAC address.
Also limit the number of udev/lib binaries that is put into the initrd
because the old initrd doesn't use all units either.
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