Fix docker cpp wasm build
here were a couple of missing dependencies in Docker that clang (strangely) needs.
FROM gcr.io/asylo-framework/asylo:buildenv-v0.4.0
-RUN apt-get -y update && apt-get install -y git curl clang-format shellcheck
+RUN apt-get -y update && apt-get install -y git curl clang-format shellcheck libncurses5 xml2
RUN git --version
RUN clang-format -version
