OvmfPkg/build.sh: remove $ADD_QEMU_HDA
$ADD_QEMU_HDA was added because QEMU used to refuse to run without a
disk. Since newer versions run without any disks, remove it.
Signed-off-by: Rebecca Cran <rebecca@bsdio.com>
Reviewed-by: Jordan Justen <jordan.l.justen@intel.com>
Reviewed-by: Philippe Mathieu-Daude <philmd@redhat.com>