Sounds like you were seeing an old emscripten SDK bug, where it compiled LLVM+clang unnecessarily and with debug info (which is very slow). Currently there sho

Sounds like you were seeing an old emscripten SDK bug, where it compiled LLVM+clang unnecessarily and with debug info (which is very slow). Currently there shouldn't be anything like that, it will download a binary build of LLVM+clang for your system. It should be ready to use immediately after that download.