Changes Emscripten SDK version to match that used to compile the default export
templates used by Godot 3.4 (in this case 2.0.25 as can be seen here:
https://github.com/godotengine/build-containers/blob/3.4/Dockerfile.javascript).
This means we no longer need to compile custom export templates when
exporting HTML5 for Godot 3.4. Exports from other Godot versions may
requiring compiling the GDNative library with a different version of the
Emscripten SDK.
Uses fork of node-pty native code for forking pseudoterminals.
Uses libuv pipe handle to communicate with the child process.
- Paves the way for cross-platform (Linux, macOS and Windows) support.
- Renames Pseudoterminal to PTY (which is much easier to type and spell :D).
- Better performance than the old Pseudoterminal node. Especially when
streaming large amounts of data such as running the `yes` command.
- Allows setting custom file, args, initial window size, cwd, env vars
(including important ones such as TERM and COLORTERM) and uid/gid
on Linux and macOS.
- Returns process exit code and terminating signal.
In a freshly cloned repo, submodule directories exist but are not
empty. Check if they are empty and update submodules. Previously,
submodules where only updated if their directories did not exist.
- Uses matrix so that build steps don't need to be defined multiple
times.
- Caches godot-cpp bindings, so they only need to be built when the
submodule version changes.
- Uploads build artifacts for linux 32/64-bit, windows 64-bit and macOS
64-bit.
