Adds a new chroot_early hook type allowing actions prior to package
installation. This is required by Ubuntu Touch and possibly other
system-image type images where we want to force a pre-defined user/group
sets.

--- live-build-3.0~a57.orig/scripts/build/lb_chroot
+++ live-build-3.0~a57/scripts/build/lb_chroot
@@ -54,6 +54,7 @@ lb chroot_archives chroot install ${*}
 # Customizing chroot
 lb chroot_linux-image ${*}
 lb chroot_preseed ${*}
+lb chroot_early_hooks ${*}
 
 for _PASS in install live
 do
--- /dev/null
+++ live-build-3.0~a57/scripts/build/lb_chroot_early_hooks
@@ -0,0 +1,70 @@
+#!/bin/sh
+
+## live-build(7) - System Build Scripts
+## Copyright (C) 2006-2012 Daniel Baumann <daniel@debian.org>
+##
+## This program comes with ABSOLUTELY NO WARRANTY; for details see COPYING.
+## This is free software, and you are welcome to redistribute it
+## under certain conditions; see COPYING for details.
+
+
+set -e
+
+# Including common functions
+( . "${LIVE_BUILD}/scripts/build.sh" > /dev/null 2>&1 || true ) || . /usr/lib/live/build.sh
+
+# Setting static variables
+DESCRIPTION="$(Echo 'execute hooks in chroot (early stage)')"
+HELP=""
+USAGE="${PROGRAM} [--force]"
+
+Arguments "${@}"
+
+# Reading configuration files
+Read_conffiles config/all config/common config/bootstrap config/chroot config/binary config/source
+Set_defaults
+
+Echo_message "Begin executing early chroot hooks..."
+
+# Requiring stage file
+Require_stagefile .build/config .build/bootstrap
+
+# Checking stage file
+Check_stagefile .build/chroot_early_hooks
+
+# Checking lock file
+Check_lockfile .lock
+
+# Creating lock file
+Create_lockfile .lock
+
+## Processing local hooks
+if Find_files config/hooks/*.chroot_early
+then
+	# Restoring cache
+	Restore_cache cache/packages.chroot
+
+	for _HOOK in config/hooks/*.chroot_early
+	do
+		# Copying hook
+		cp "${_HOOK}" chroot/root
+
+		# Making hook executable
+		if [ ! -x chroot/root/"$(basename ${_HOOK})" ]
+		then
+			chmod +x chroot/root/"$(basename ${_HOOK})"
+		fi
+
+		# Executing hook
+		Chroot chroot "/root/$(basename ${_HOOK})" || { Echo_error "${_HOOK} failed (exit non-zero). You should check for errors."; exit 1 ;}
+
+		# Removing hook
+		rm -f chroot/root/"$(basename ${_HOOK})"
+	done
+
+	# Saving cache
+	Save_cache cache/packages.chroot
+
+	# Creating stage file
+	Create_stagefile .build/chroot_early_hooks
+fi