dib: source dib "die" script in some phases

Source the "die" script, part of the diskimage-builder library, when
running hooks that run outside the guest chroot.  This is what
disk-image-create does, and scripts expect to use the "die" function
without sourcing the "die" script containing it.

dib/dib.ml

@@ -124,6 +124,8 @@ if [ -d $ENVIRONMENT_D_DIR ] ; then
     done
 fi
 
+source $_LIB/die
+
 $target_dir/$script
 "
     (if debug >= 1 then "set -x\n" else "")
@@ -206,6 +208,7 @@ export TMP_IMAGE_DIR=$mysysroot/tmp/aux
 
 if [ -n \"$mysysroot\" ]; then
   export PATH=$mysysroot/tmp/aux/fake-bin:$PATH
+  source $_LIB/die
 else
   export PATH=\"$PATH:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin\"
 fi