/sbin/mkinitrd in mkinitrd-3.4.43-1 contains code that looks like this:

  awk '/^md[0-9][0-9]*[ 	]*:/ { print $4 }' /proc/mdstat

Unfortunately, it appears that the version of awk in gawk-3.1.2-1 refuses to
read any data from a file if stat on the file returns a size of 0:

  $ awk '/^md[0-9][0-9]*[       ]*:/ { print $4 }' /proc/mdstat
  $ cat /proc/mdstat | awk '/^md[0-9][0-9]*[    ]*:/ { print $4 }'  
  raid1
  raid1
  raid1
  raid1
  $ 

Now, it could be argued that this is a bug in gawk, and indeed, I think I'll
file a bug report about it, but still, I think it would be best for mkinitrd to
be resilient in the face of this problem by using the "cat" technique shown
above.  I'll attach a patch.