source: downloaded pkgs to a clean directory rather than chroot root

Closes: #952931

scripts/build/source_debian

@@ -131,19 +131,9 @@ case "${LB_MODE}" in
 		;;
 esac
 
-MISSING=""
-while read -r PACKAGE
-do
-	if ! Chroot chroot "apt-get ${APT_OPTIONS} --download-only source ${PACKAGE}"
-	then
-		MISSING="${MISSING} ${PACKAGE}"
-	fi
-done < source-selection.txt
-rm -f source-selection.txt
+mkdir -p chroot/source.pkgs
 
-if [ -n "${MISSING}" ]
-then
-	cat > source/missing-source.txt << EOF
+cat > chroot/missing-source.txt << EOF
 This file contains the list of binary packages that are installed on the "live"
 system (to which this source disc is a companion) for which a corresponding
 source package is not included on this disc. This may be because the binary
@@ -152,14 +142,34 @@ the source package available was not the same as that of the binary.
 
 EOF
 
-	for PACKAGE in ${MISSING}
-	do
-		Chroot chroot "dpkg -l ${PACKAGE}" | tail -n1 >> source/missing-source.txt
-	done
+cat > chroot/source-download.sh << EOF
+#!/bin/sh
+cd source.pkgs
+PACKAGE="\${1}"
+if ! apt-get ${APT_OPTIONS} --download-only source \${PACKAGE}
+then
+	dpkg -l \${PACKAGE} | tail -n1 >> ../missing-source.txt
+	touch ../missing-source-some
+fi
+EOF
+
+while read -r PACKAGE
+do
+	Chroot chroot "sh source-download.sh ${PACKAGE}" || true
+done < source-selection.txt
+rm -f source-selection.txt
+rm -f chroot/source-download.sh
+
+if [ -e chroot/missing-source-some ]
+then
+	mv chroot/missing-source.txt source/missing-source.txt
+	rm -f chroot/missing-source-some
+else
+	rm -f chroot/missing-source.txt
 fi
 
 # Sort sources
-for DSC in chroot/*.dsc
+for DSC in chroot/source.pkgs/*.dsc
 do
 	SOURCE="$(sed -n 's|^Source: ||p' ${DSC} 2>/dev/null || :)"
 	# The sed may fail if multiple dsc files exist for same source, as the
@@ -180,9 +190,11 @@ do
 	mkdir -p source/debian/"${LETTER}"/"${SOURCE}"
 
 	# Move files
-	mv chroot/"${SOURCE}"_* source/debian/"${LETTER}"/"${SOURCE}"
+	mv chroot/source.pkgs/"${SOURCE}"_* source/debian/"${LETTER}"/"${SOURCE}"
 done
 
+rmdir --ignore-fail-on-non-empty chroot/source.pkgs
+
 # Reverting apt sources again
 if [ -e chroot/etc/apt/sources.list.d/progress-linux.list.orig ]
 then