bootupd: Enable static GRUB config migration

See: coreos/bootupd#790
See: coreos/bootupd#789
See: https://gitlab.com/fedora/ostree/sig/-/issues/35

bootupd.yaml

@@ -12,6 +12,13 @@ postprocess:
     # Transforms /usr/lib/ostree-boot into a bootupd-compatible update payload
     /usr/bin/bootupctl backend generate-update-metadata
 
+    # Enable migration to a static GRUB config
+    install -dm0755 /usr/lib/systemd/system/bootloader-update.service.d
+    cat > /usr/lib/systemd/system/bootloader-update.service.d/migrate-static-grub-config.conf << 'EOF'
+    [Service]
+    ExecStart=/usr/bin/bootupctl migrate-static-grub-config
+    EOF
+
     echo "enable bootloader-update.service" > /usr/lib/systemd/system-preset/81-atomic-desktop.preset
 
     # Turn permissive mode on for bootupd until all SELinux issues are fixed