We can now do away with the `iceunpack`/`icebram`/`icepack` dance and
simply patch files on the fly. This should simplify development,
since you only need two files (the bitstream and the replacement rom),
rather than four files (the bitstream, the replacement rom, the
random contents, and the output file).
Signed-off-by: Sean Cross <sean@xobs.io>
