emscripten-core/emscripten ? reverse-engineered prompt

I want to get this project building from a fresh clone and make sure the basic compiler workflow works end to end.

Please set it up so I can run the bootstrap and build steps without guessing, then verify that I can compile a simple C or C plus plus file into WebAssembly and run the output in Node or a browser style HTML page. If anything is missing or unclear, update the docs with the simplest steps a new contributor would need, including any required dependencies and the first command to try.

Also check that the main command line tools like emcc work as expected after the build, and add a small smoke test or example if that helps prove everything is working. If you need to look up current setup details online, go ahead and do that.