Add management of arch detection from d-i in isolinux

debian/changelog

@@ -18,6 +18,7 @@ debian-cd (3.1.18) UNRELEASED; urgency=medium
   [ Didier Raboud ]
   * For stretch, swap amd64 and i386 to let the first be the norm, and the
     latter be the special case, this copes with the similar change in d-i
+  * Add management of arch detection from d-i in isolinux
 
  -- Steve McIntyre <93sam@debian.org>  Mon, 20 Apr 2015 12:36:57 +0100
 

tools/boot/stretch/boot-x86

@@ -296,6 +296,11 @@ if [ "$BOOT_BIOS" = 1 ] ; then
     cp -f $CDDIR/../syslinux/usr/lib/syslinux/modules/bios/libcom32.c32 boot$N/isolinux/
     cp -f $CDDIR/../syslinux/usr/lib/syslinux/modules/bios/libutil.c32 boot$N/isolinux/
 
+    if [ ! -z "$MULTIARCH" ]; then
+        # Mandatory for 64bits capability detection
+        cp -f $CDDIR/../syslinux/usr/lib/syslinux/modules/bios/ifcpu64.c32 boot$N/isolinux/
+    fi
+
     # If we don't have grub stuff from d-i, tell xorriso to add a
     # partition offset for the isohybrid code
     if [ ! -d boot$N/isolinux/grub ] || [ $BOOT_EFI = 0 ] ; then
@@ -360,6 +365,9 @@ if [ -z "$MULTIARCH" ]; then
     # that does not have both amd64 and i386 dirs.
     find boot$N/isolinux/ -name "x86*.cfg" -delete
 else
+    # Use the syslinux.cfg with architecture detection
+    mv boot$N/isolinux/x86syslinux.cfg boot$N/isolinux/isolinux.cfg
+
     # Set up isolinux dir for multi-arch
     grep -lr '%install[-x86]*%' boot$N/isolinux/* | \
         xargs -r sed -i -e "s|%install%|$INSTALLDIR_amd64|" \