Add my hacky script to rebuild dependencies, in case this is needed again in the future.
Emscripten changed ABI for .a files. Rebuild all deps, updating to current version. Switch Emscripten to incoming branch as it's not working on master right now. Added simple script for rebuilding deps in case it becomes necessary again. Switch builds to always use -g flag, per Emscripten's warnings. Undefine native client defines so that it builds (Emscripten switched to NaCl alignment, macro got defined as a side-effect).