Enable wasm source maps.

[yurydelendik]

Creates source map file for ".wasm" during compilation with -g4. Also adds --source-map-base option to provide a complete solution -- currently the .wasm file must contain sourceMappingURL section to make it work (per WebAssembly/design#1051).

The patch requires binaryen with patch WebAssembly/binaryen#1017

The example output can be found at https://github.com/yurydelendik/wasm-source-map-emscripten/

[yurydelendik]

/cc @dschuff

[kripken]

Overall looks nice, just one minor comment above, and also, please update the binaryen tag to 34 so that it uses a version with source maps support (I pushed that tag to binaryen now, so you just need to edit tools/ports/binaryen.py).

[kripken]

since this method is just for js and not wasm, how about renaming it to emit_js_source_maps?

[yurydelendik]

please update the binaryen tag to 34 so that it uses a version with source maps support

Fixed

[kripken]

Thanks, looks good. Although I notice now that this doesn't have a test. Let's merge this in for now, but can you please add one later?

[kripken]

@yurydelendik this broke binaryen2.test_source_map. perhaps the test needs to be updated for the new format somehow?

[yurydelendik]

the test needs to be updated for the new format somehow?

Yes, the test_source_map test needs to be updated for binaryen* tests to provide right map file name. Also, source-map package is a little bit outdated, e.g. it requires 'file' attribute which is optional. (I will submit patch after I'll done testing it)