gpt: trigger udev after marking hybrid mbr partitions as bootable

Even though we don't depend on the MBR bootable flag in the following
steps, not running udevadm trigger and waiting for settle can cause
/dev/disk/by-partlabel entries to be absent when formatting filesystems
immediately after modifying the partition table.

Author: sysedwinistrator

lib/types/gpt.nix

@@ -229,6 +229,8 @@ in
                             ''}
                             ${lib.optionalString hp.config.mbrBootableFlag ''
                               sfdisk --label-nested dos --activate "${parent.device}" ${(toString partition.config._index)}
+                              udevadm trigger --subsystem-match=block
+                              udevadm settle --timeout 120
                             ''}
                           '';
                         };