ci: link systemd-keyutil into place

The mkosi action.yaml links systemd main, and instealls an hard-coded
set of binaries. ukify now depends on the new systemd-keyutil, which
cannot be in that list. Link it manually.

(cherry picked from commit 8f24348)
(cherry picked from commit 150b961)

.github/workflows/mkosi.yml

@@ -129,6 +129,8 @@ jobs:
         CopyFiles=/
         Minimize=guess
         EOF
+        sudo ln -svf "$(dirname "$(readlink /usr/bin/bootctl)")/systemd-keyutil" /usr/lib/systemd/systemd-keyutil
+        /usr/lib/systemd/systemd-keyutil --version
 
     - name: Generate secure boot key
       run: mkosi genkey