No longer parse emscripten/emsdk config to detect emcc/node paths.
Use WhereIs to find "emcc" and "node", look for "node_modules" in "emcc"
path.
(cherry picked from commit 7998745237)
- Refactored the Engine code, splitted across files.
- Use MODULARIZE option to build emscripten code into it's own closure.
- Optional closure compiler run for JS and generated code.
- Enable lto support (saves ~2MiB in release).
- Can now build with tools=yes (not much to see yet).
- Dropped some deprecated code for older toolchains.
- Add onExit, and onExecute JS function.
- Add files drag and drop support.
- Add support for low precessor usage mode (via offscreen render, swap).
