Fix handlinkg of LOGOPNG when we've got "doppelganer" initramfs files

Backported from unstable, needed for debian-edu builds

debian/changelog

@@ -4,6 +4,8 @@ debian-cd (3.1.17-jessie) UNRELEASED; urgency=medium
     + Remove mention of desktop choice from yaboot boot messages
       (Closes: #783569)
     + Remove uncompressed translation files after compressing them
+    + Fix handlinkg of LOGOPNG when we've got "doppelganer" initramfs
+      files
 
  -- Steve McIntyre <93sam@debian.org>  Mon, 20 Apr 2015 12:36:57 +0100
 

tools/boot/jessie/boot-x86

@@ -405,7 +405,10 @@ if [ "$LOGOPNG" ] ; then
     mkdir -p $INITRDDIR
     (
         cd $INITRDDIR
-        gunzip $GTKINITRDGZ
+        # There may be multiple hardlinks to the initrd.gz, so
+        # explicitly break the links here
+        zcat $GTKINITRDGZ > $GTKINITRD
+        rm -f $GTKINITRDGZ
         mkdir -p $INITRDDIR/usr/share/graphics
         cp $LOGOPNG $INITRDDIR/usr/share/graphics/logo_debian.png
         echo usr/share/graphics/logo_debian.png | \