> Emscripten builds taking between 10 and 50 times longer to compile than the native code ones.

Hey, this is fatal. With this massively long iteration time, you can't run actual big projects. Only executing 1,000,000 lines of C++ code is not enough. We care the build time as well as the perforamnce.

BTW, have you heard that the next Haswell processors can get only 5% performance improvement? We should assume that we have no free lunch anymore. One of the UNIX philosophies is already broken.