Creating a bootable Linux image using extlinux

I am helping a friend setup a bootable Linux image using extlinux. Here is what I have so far, but using qemu-system-x86_64, I am not able to get it to boot this image. The options to qemu-system-x86_64 is just -m 2048 -drive format=raw,file=myapp.img. The qemu-system-x86_64 just says 'Booting from Hard Disk ...'. I am wondering what am I doing wrong. The kernel and initrd boot up just fine in qemu. The bootable image is intended for an old non-UEFI system.

    #!/bin/sh -ex

    APP=myapp
    IMG=${APP}.img
    KERNEL=$1
    INITRD=$2

    MNTPNT=/media/usb
    SIZE=1G

    qemu-img create -f raw  $IMG $SIZE
    sudo dd if=/usr/lib/syslinux/mbr/mbr.bin of=$IMG conv=notrunc bs=440 count=1
    parted -s $IMG mklabel msdos
    parted -s -a none $IMG mkpart primary ext4 0 $SIZE

    lodev=$(losetup -f)
    sudo losetup $lodev $IMG
    sudo partx -a $lodev
    sudo mkfs.ext4 ${lodev}p1

    sudo mount ${lodev}p1 $MNTPNT
    sudo mkdir -p $MNTPNT/boot/extlinux
    sudo cp extlinux.conf $MNTPNT/boot/extlinux/
    sudo cp /usr/lib/syslinux/memdisk $MNTPNT/boot/extlinux/
    sudo cp /usr/lib/syslinux/modules/bios/* $MNTPNT/boot/extlinux/
    sudo cp $KERNEL $MNTPNT/boot/
    sudo cp $INITRD $MNTPNT/boot/
    sudo extlinux --install $MNTPNT/boot/extlinux/
    sudo umount $MNTPNT

    sudo partx -d $lodev
    sudo losetup -d $lodev