Build wasm for Draw Harness

This project helps you build WASM files for this project: https://github.com/gkv311/occt-draw

How to do

1. Install the Ddocker and BuildKit. The latest version of Docker has been integrated with BuildKit.
2. Clone this project.
3. Run

   `DOCKER_BUILDKIT=1 docker build -o type=local,dest=WASM_OUTPUT_PATH .` 

   Build the single-threaded DRAWEXE.

   `DOCKER_BUILDKIT=1 docker build -o type=local,dest=WASM_OUTPUT_PATH --build-arg pthread=-pthread .` 

   Build multi-threaded DRAWEXE.