sid builds broken because of new syslinux

[Baurzhan Muftakhidinov <baurthefirst@gmail.com>]

Good day,

Yesterday I tried to build an Debian sid-based image
(iso-hybrid), which failed to pack to iso image
with xorriso complaining to absent isohdpfx.bin file.

Please find example patch below, it should be applied if
syslinux 6 is being used
(Not sure how to handle jessie builds with syslinux 4).

However, then live-builds complain to missing
isolinux.bin file, and I have noticed that links in
/usr/share/live/build/bootloaders/isolinux/
are all broken, and even after installing isolinux
package and correcting the links in folder above,
xorriso couldn't find the isolinux.bin file.

-------- snip -----

diff --git a/scripts/build/binary_iso b/scripts/build/binary_iso
index 9b4d6ea..43e3248 100755
--- a/scripts/build/binary_iso
+++ b/scripts/build/binary_iso
@@ -57,7 +57,7 @@ Check_package chroot/usr/bin/xorriso xorriso

 if [ "${LIVE_IMAGE_TYPE}" = "iso-hybrid" ]
 then
-       Check_package chroot/usr/lib/syslinux/isohdpfx.bin syslinux-common
+       Check_package chroot/usr/lib/syslinux/mbr/isohdpfx.bin syslinux-common
 fi

 # Restoring cache
@@ -78,7 +78,7 @@ XORRISO_OPTIONS="-R -r -J -joliet-long -l -cache-inodes"
 # Handle xorriso live-build specific options
 if [ "${LIVE_IMAGE_TYPE}" = "iso-hybrid" ]
 then
-       XORRISO_OPTIONS="${XORRISO_OPTIONS} -isohybrid-mbr
/usr/lib/syslinux/isohdpfx.bin -partition_offset 16"
+       XORRISO_OPTIONS="${XORRISO_OPTIONS} -isohybrid-mbr
/usr/lib/syslinux/mbr/isohdpfx.bin -partition_offset 16"
 fi

 if [ "${_QUIET}" = "true" ]