prefer installed extlinux

bootfiles/bootinst.sh

@@ -11,8 +11,14 @@ cd "$BOOT"
 PART="$(df . | tail -n 1 | tr -s " " | cut -d " " -f 1)"
 DEV="$(echo "$PART" | sed -r "s:[0-9]+\$::" | sed -r "s:([0-9])[a-z]+\$:\\1:i")"   #"
 
-# install syslinux bootloader
-./extlinux.exe --install $BOOT
+# Try to use installed extlinux binary and fallback to extlinux.exe only
+# if no installed extlinux is not found at all.
+EXTLINUX="$(which extlinux 2>/dev/null)"
+if [ "$EXTLINUX" = "" ]; then
+   EXTLINUX="./extlinux.exe"
+fi
+
+"$EXTLINUX" --install "$BOOT"
 
 if [ $? -ne 0 ]; then
    echo "Error installing boot loader."