message: reduce the image size of the Docker containers
  install later required components depending on rust-toolchain.toml
diff: @@ -9,8 +9,8 @@ RUN apt-get update && \
  # Install Rust toolchain
  RUN curl https://sh.rustup.rs -sSf | sh -s -- -y --default-toolchain nightly --profile minimal
  RUN /root/.cargo/bin/cargo install cargo-download
  -RUN /root/.cargo/bin/rustup component add rust-src
  -RUN /root/.cargo/bin/rustup component add llvm-tools-preview
  +#RUN /root/.cargo/bin/rustup component add rust-src
  +#RUN /root/.cargo/bin/rustup component add llvm-tools-preview
  ENV PATH="/root/.cargo/bin:/root/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/bin/:${PATH}"
  