* allow the bazel toolchain to output html files
* allow for cc_binary rule names to end in .js
* fix python name
* continue to call emcc instead of em++ for now
* small cleanup
Co-authored-by: Mitch Foley <mitchfoley@chromium.org>
This change comes with fairly major change to the bazel toolchain.
- Use pre-built cache that comes with emsdk
- Mark cache as readonly using FROZEN_CACHE
- Pass `--sysroot` to match upstream emscripten change
