Features:
+* in sd-stub: optionally add support for a new PE section .keyring or so that
+ contains additional certificates to include in the Mok keyring, extending
+ what shim might have placed there. why? let's say I use "ukify" to build +
+ sign my own fedora-based UKIs, and only enroll my personal lennart key via
+ shim. Then, I want to include the fedora keyring in it, so that kmods work.
+ But I might not want to enroll the fedora key in shim, because this would
+ also mean that the key would be in effect whenever I boot an archlinux UKI
+ built the same way, signed with the same lennart key.
+
* resolved: take possession of some IPv6 ULA address (let's say
fd00:5353:5353:5353:5353:5353:5353:5353), and listen on port 53 on it for the
local stubs, so that we can make the stub available via ipv6 too.