changes to be able to get *working* isolinux result

do not remove tarball until build has finished, as the build process is
fragile and dependencies that are needed are listed nowhere, meaning i
have to download several times as appeared some tool or header was
missing

ignoring and hiding errors is bad and evil, instead stop on errors so
user can see error and try to fix it

additionally fill out requirements in comment. really should test for
program existence or headers to be very nice with it

tools/isolinux.bin.update

@@ -2,6 +2,9 @@
 
 # This script will update the file ../bootfiles/isolinux.bin to match
 # your LiveKit name used in ../.config
+# Requires: wget, tar, gzip, make, gcc, nasm, perl, glibc-devel, libuuid-devel (e2fsprogs)
+
+set -e
 
 PKG=syslinux-4.06
 PKGTGZ=$PKG.tar.gz
@@ -10,20 +13,23 @@ DL="http://www.kernel.org/pub/linux/utils/boot/syslinux/$PKGTGZ"
 . ../.config
 
 # download, unpack, and patch syslinux
+if [ ! -d $PKG ]; then
+	rm -rf $PKG
 	wget -c "$DL"
 	tar -xf $PKGTGZ
-rm $PKGTGZ
+fi
 
 cd $PKG
 
 sed -i -r "s:/boot/syslinux:/$LIVEKITNAME/boot:" core/fs/iso9660/iso9660.c
 sed -i -r "s:/boot/syslinux:/$LIVEKITNAME/boot:" core/fs/lib/loadconfig.c
 
-make -i
-cp core/isolinux.bin ../../bootfiles/isolinux.bin
+make
+cp -p core/isolinux.bin ../../bootfiles/isolinux.bin
 
 echo
 echo "Copying isolinux.bin to $(realpath ../../bootfiles/isolinux.bin)"
 
 cd ..
 rm -Rf $PKG
+rm $PKGTGZ