grub2|loopback: avoid perl for live entry creation, use temp file

instead of cramming the live entries into a string via a layer of functions
for terminating entries with newlines, which we then have to run through
perl to tweak the newlines for correct use with sed... let's write the
entries to a temp file, then use that file in the sed replacement.

the helper functions injecting newlines to the end of entries as they were
built into a long string have obviously become unnecessary and so were
removed. one function was renamed for reasons of consistency and clarity.

the file is initially deleted before use for reasons of wanting to bullet
proof the codebase to work properly under conditions of recovering from
failure/cancellation, `--force` re-running and such.

this removes the last use of perl.

Gbp-Dch: Short

scripts/build/binary_loopback_cfg

@@ -42,19 +42,15 @@ Check_crossarchitectures
 
 _TARGET="binary/boot/grub"
 
-# Variable used to embed newlines
-NL="
-"
-
 # Local functions
-Grub_menu_entry() {
+Grub_live_menu_entry() {
 	local LABEL="$1"
 	local KERNEL="$2"
 	local INITRD="$3"
 	local APPEND="$4"
 	local HOTKEY="${5:+ --hotkey=$5}"
 
-	cat <<END
+	cat >> "${LIVE_ENTRIES_TMP}" <<END
 menuentry "${LABEL}"${HOTKEY} {
 	linux	$KERNEL $APPEND
 	initrd	$INITRD
@@ -62,11 +58,6 @@ menuentry "${LABEL}"${HOTKEY} {
 END
 }
 
-Grub_live_entry ()
-{
-	LINUX_LIVE="${LINUX_LIVE}$(Grub_menu_entry "$@")$NL"
-}
-
 Grub_live_autodetect_menu_entry ()
 {
 	local LABEL="${1}"
@@ -75,7 +66,8 @@ Grub_live_autodetect_menu_entry ()
 	local _686_KERNEL="${4}"
 	local _686_INITRD="${5}"
 	local APPEND="${6}"
-	cat <<END
+
+	cat >> "${LIVE_ENTRIES_TMP}" <<END
 # Autodetect if amd64 is supported
 menuentry "$LABEL" {
 	if cpuid -l; then
@@ -89,11 +81,6 @@ menuentry "$LABEL" {
 END
 }
 
-Grub_live_autodetect_entry ()
-{
-	LINUX_LIVE="${LINUX_LIVE}$(Grub_live_autodetect_menu_entry "$@")$NL"
-}
-
 # User config replacement/additional files
 _SOURCE_USER="config/bootloaders/grub-pc"
 
@@ -132,7 +119,11 @@ KERNEL_LIVE="/${INITFS}/${DEFAULT_KERNEL}"
 INITRD_LIVE="/${INITFS}/${DEFAULT_INITRD}"
 APPEND_LIVE="${LB_BOOTAPPEND_LIVE} findiso=\${iso_path}"
 
-# Assembling kernel configuration
+# Ensure fresh live entries
+LIVE_ENTRIES_TMP="${_TARGET}/live.cfg.tmp"
+rm -f "${LIVE_ENTRIES_TMP}"
+
+# Assemble live menu entries
 _AMD64_686_NUMBER="0"
 
 for _FLAVOUR in ${LB_LINUX_FLAVOURS}; do
@@ -148,7 +139,7 @@ if [ "${_AMD64_686_NUMBER}" -ge 2 ] ; then
 	_686_KERNEL="$(basename chroot/boot/vmlinuz-*686)"
 	_686_INITRD="initrd.img-$(echo ${_686_KERNEL} | sed -e 's|vmlinuz-||')"
 
-	Grub_live_autodetect_entry "Live system (autodetect)" \
+	Grub_live_autodetect_menu_entry "Live system (autodetect)" \
 		"/${INITFS}/${AMD64_KERNEL}" \
 		"/${INITFS}/${AMD64_INITRD}" \
 		"/${INITFS}/${_686_KERNEL}" \
@@ -156,7 +147,7 @@ if [ "${_AMD64_686_NUMBER}" -ge 2 ] ; then
 		"${APPEND_LIVE}"
 
 	if [ "${LB_BOOTAPPEND_LIVE_FAILSAFE}" != "none" ]; then
-		Grub_live_autodetect_entry "Live system (autodetect) (fail-safe mode)" \
+		Grub_live_autodetect_menu_entry "Live system (autodetect) (fail-safe mode)" \
 			"/${INITFS}/${AMD64_KERNEL}" \
 			"/${INITFS}/${AMD64_INITRD}" \
 			"/${INITFS}/${_686_KERNEL}" \
@@ -164,13 +155,13 @@ if [ "${_AMD64_686_NUMBER}" -ge 2 ] ; then
 			"${LB_BOOTAPPEND_LIVE_FAILSAFE}"
 	fi
 else
-	Grub_live_entry "Live system" \
+	Grub_live_menu_entry "Live system" \
 		"/${INITFS}/${DEFAULT_KERNEL}" \
 		"/${INITFS}/${DEFAULT_INITRD}" \
 		"${APPEND_LIVE}" \
 		"l"
 	if [ "${LB_BOOTAPPEND_LIVE_FAILSAFE}" != "none" ]; then
-		Grub_live_entry "Live system (fail-safe mode)" \
+		Grub_live_menu_entry "Live system (fail-safe mode)" \
 			"/${INITFS}/${DEFAULT_KERNEL}" \
 			"/${INITFS}/${DEFAULT_INITRD}" \
 			"${LB_BOOTAPPEND_LIVE_FAILSAFE}"
@@ -186,13 +177,13 @@ if [ $_COUNT -gt 1 ]; then
 	for KERNEL in chroot/boot/vmlinuz-*; do
 		VERSION="$(basename ${KERNEL} | sed -e 's|vmlinuz-||')"
 
-		Grub_live_entry "Live system, kernel ${VERSION}" \
+		Grub_live_menu_entry "Live system, kernel ${VERSION}" \
 			"/${INITFS}/$(basename ${KERNEL})" \
 			"/${INITFS}/initrd.img-${VERSION}" \
 			"${APPEND_LIVE}"
 
 		if [ "${LB_BOOTAPPEND_LIVE_FAILSAFE}" != "none" ]; then
-			Grub_live_entry "Live system, kernel ${VERSION} (fail-safe mode)" \
+			Grub_live_menu_entry "Live system, kernel ${VERSION} (fail-safe mode)" \
 				"/${INITFS}/$(basename ${KERNEL})" \
 				"/${INITFS}/initrd.img-${VERSION}" \
 				"${LB_BOOTAPPEND_LIVE_FAILSAFE}"
@@ -200,6 +191,11 @@ if [ $_COUNT -gt 1 ]; then
 	done
 fi
 
+# Replace placeholder with compiled live entries temporarily held in live.cfg.tmp
+sed -i -e "/@LINUX_LIVE@/ r ${LIVE_ENTRIES_TMP}" "${_TARGET}"/*.cfg
+sed -i -e "/LINUX_LIVE/ r ${LIVE_ENTRIES_TMP}" "${_TARGET}"/*.cfg #backwards compatibility
+rm -f "${LIVE_ENTRIES_TMP}"
+
 # Assembling debian-installer configuration
 if [ "${LB_DEBIAN_INSTALLER}" != "none" ]; then
 	ENABLE_INSTALL_MENU="true"
@@ -241,17 +237,12 @@ else
 	rm -f "${_TARGET}"/memtest.cfg
 fi
 
-escape_for_sed() {
-	echo -n "$1" | perl -npe 's/\n/\\n/gm'
-}
-
 # These must be held in variables to avoid mistake by checkbashisms
 LINUX_INSTALL="source /boot/grub/install_start.cfg"
 LINUX_ADVANCED_INSTALL="source /boot/grub/install.cfg"
 
 # Those without '@' markers are for backwards compatibility
 sed -i \
-    -e "s|@LINUX_LIVE@|$(escape_for_sed "${LINUX_LIVE}")|" \
     -e "s|@KERNEL_GI@|${KERNEL_GI}|" \
     -e "s|@INITRD_GI@|${INITRD_GI}|" \
     -e "s|@APPEND_GI@|${APPEND_GI}|" \
@@ -269,7 +260,6 @@ sed -i \
     -e "s|@ENABLE_MEMTEST@|${ENABLE_MEMTEST}|" \
     -e "s|@MEMTEST_BIN@|${MEMTEST_BIN}|" \
     -e "s|@MEMTEST_VERSION@|${LB_MEMTEST}|" \
-    -e "s|LINUX_LIVE|$(escape_for_sed "${LINUX_LIVE}")|" \
     -e "s|LINUX_INSTALL|${LINUX_INSTALL}|" \
     -e "s|LINUX_ADVANCED_INSTALL|${LINUX_ADVANCED_INSTALL}|" \
     -e "s|MEMTEST|${MEMTEST}|" \