Emscripten 1.39 support (#4803)

This is a heads up that we’ll very soon upgrade to Emscripten 1.39.16.
It will make the executable a bit smaller (~-13%) using the new llvm backend for Wasm. It will also streamline the development pipeline for our new contributors, and make it easier for us to update in the future.

We expect this upgrade to be done in 1.2.170.

What you as an extension developer needs to do, is check that you extension works with the new compiler. Our previous version was 1.38.12. If you had prebuilt library files (.a) you will need to recompile these.

If you are a user of native extensions and you target HTML5, you should test as well, so that we can find the extensions that needs upgrading, and you won’t get any surprises when upgrading to the next release.

The beta will arrive in two weeks, until then you can test with these builds:

Test build server: https://build-stage.defold.com

Emscripten release notes/transition guide:

Notable changes:

  • v1.38.27:
    • Replace Pointer_stringify with UTF8ToString
  • v1.37.27
    • Replace Runtime.func with func

EDIT: The link to the issue #4803