dnasdw/3dstool — reverse-engineered prompt

Build me a cross platform C command line tool for working with Nintendo 3DS ROM files. I want one executable called 3dstool that can extract and create ROM containers, and handle common pieces like NCSD, NCCH, CXI, CFA, ExeFS, RomFS, banners, and compression formats like LZ77, Huffman, Yaz0, and BLZ.

Please make it usable from the terminal with a clear help screen, sensible options, and examples for extracting a game file into folders and rebuilding it again. It should support encryption handling where possible, plus diff and patch if that fits the ROM workflow.

Set it up with CMake so it builds on Windows, Linux, and macOS, with simple 64 bit and 32 bit build instructions. Use common dependencies like OpenSSL, curl, and iconv if needed. Keep the README practical and short enough that someone can compile it and run the main commands without guessing.