* (bazel) Set @platforms//os:emscripten for platform_wasm
* (bazel) Set @platforms//os:emscripten for platform_wasm
* (bazel) Set @platforms//os:emscripten for platform_wasm
In the past the instructions were to copy `emscripten_toolchain` into the project dir, now it downloads emsdk as a package so the `bazelrc` part has to refer to `@emsdk`.