private void writeEndMark() throws IOException {
        ByteUtils.writeUnsignedIntLE(out, 0);
        // TODO implement content checksum, update flg.validate()
    }
Similar to the {@link #writeBlock()} method. Writes a 0-length block (without block checksum) to signal the end
of the block stream.

@throws IOException
clients/src/main/java/org/apache/kafka/common/compress/Lz4BlockOutputStream.java