Create a symlink for the live image's base loop device

It is useful to know that loop device that the live image's / is mounted
from. Make a /run/initramfs/live-baseloop symlink that points to it.

Edited-By: harald@redhat.com: changed /dev/live-baseloop
                              to /run/initramfs/live-baseloop

modules.d/90dmsquash-live/dmsquash-live-root

@@ -200,6 +200,9 @@ if [ -n "$ROOTFLAGS" ]; then
     ROOTFLAGS="-o $ROOTFLAGS"
 fi
 
+if [ -b "$BASE_LOOPDEV" ]; then
+    ln -s $BASE_LOOPDEV /dev/live-baseloop
+fi
 ln -s /dev/mapper/live-rw /dev/root
 printf '/bin/mount %s /dev/mapper/live-rw %s\n' "$ROOTFLAGS" "$NEWROOT" > $hookdir/mount/01-$$-live.sh