Bazel add html support (#765)

* 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>

bazel/emscripten_toolchain/wasm_cc_binary.bzl

@@ -74,6 +74,7 @@ def _wasm_binary_impl(ctx):
         ctx.outputs.data,
         ctx.outputs.symbols,
         ctx.outputs.dwarf,
+        ctx.outputs.html,
     ]
 
     ctx.actions.run(
@@ -103,6 +104,7 @@ def _wasm_binary_outputs(name, cc_target):
         "data": "{}/{}.data".format(name, basename),
         "symbols": "{}/{}.js.symbols".format(name, basename),
         "dwarf": "{}/{}.wasm.debug.wasm".format(name, basename),
+        "html": "{}/{}.html".format(name, basename),
     }
 
     return outputs