make overlay scripts use kernel modules and executables relative to pwd in preparison for 9p

rootfs_overlay/rand_check_poweroff.sh

@@ -1,6 +1,6 @@
 #!/bin/sh
 set -ex
-/rand_check.out
+./rand_check.out
 
 # Check if network is being replayed.
 # https://superuser.com/questions/635020/how-to-know-current-time-from-internet-from-command-line-in-linux
@@ -9,4 +9,4 @@ set -ex
 
 # busybox's poweroff panics, TODO why. Likely tries to kill shell.
 # So just use our super raw command.
-/poweroff.out
+./poweroff.out