Add ninja to wasm32 build

Author: workingjubilee

ci/docker/wasm32-unknown-unknown/Dockerfile

@@ -8,6 +8,7 @@ RUN apt-get update -y && apt-get install -y --no-install-recommends \
   git \
   libc6-dev \
   make \
+  ninja \
   python-is-python3 \
   xz-utils