Update config to use icudtb.dat if the byteorder is big
endian, this will work for other big endian platforms
such as PPC and s390.
Original CL for BE support: https://codereview.chromium.org/2162393003

R=jshin@chromium.org
BUG=v8:5567

Review URL: https://codereview.chromium.org/2434153002 .