[Build] Very basic GitHub Actions workflow for Emscripten(WASM) build with vcpkg

[luncliff]

Description

• Create emscripten.yml which runs WebAssembly build with GitHub Actions
  • Need more works to cover various WASM build options.
    This is the minimal work based on azure-pipelines/templates/linux-wasm-ci.yml
• Change build.py to support both --use_vcpkg and --build_wasm
• When using vcpkg, the triplet wasm32-emscripten.cmake will be used.
  • Because this triplet is using VCPKG_CHAINLOAD_TOOLCHAIN_FILE, we can't use VCPKG_CXX_FLAGS or VCPKG_LINKER_FLAGS to customize build details of the external libraries in vcpkg.json
  • I used EMCC_CFLAGS to apply emcc compiler options globally

Without EMCC_CFLAGS customization, we will get the linkage errors.

2025-01-31T18:35:38.8323800Z [ 30%] Building CXX object CMakeFiles/onnxruntime_framework.dir/__w/onnxruntime/onnxruntime/onnxruntime/core/framework/stream_execution_context.cc.o
2025-01-31T18:35:38.9889222Z wasm-ld: error: --shared-memory is disallowed by gtest-all.cc.o because it was not compiled with 'atomics' or 'bulk-memory' features.
2025-01-31T18:35:39.0098272Z em++: error: '/emsdk/upstream/bin/wasm-ld @/tmp/emscripten_mgozcgg0.rsp.utf-8' failed (returned 1)

Warning

Currently, wasm32-emscripten fails the unit test phase of build.py, with "out of memory" exception.

I guess it's kind of onnxruntime_ENABLE_WEBASSEMBLY_MEMORY64 issue.

Motivation and Context

I don't have a WASM experience. Feel free to advice :D

• Help [Build] Better support for vcpkg #23158

References

• https://hub.docker.com/r/emscripten/emsdk
• https://emscripten.org/docs/tools_reference/emcc.html
• https://github.com/emscripten-core/emscripten/blob/3.1.74/emcc.py
• https://emscripten.org/docs/tools_reference/settings_reference.html
• https://github.com/emscripten-core/emscripten/blob/3.1.74/tools/settings.py