Dockerfile fixed. (#308)

* Dockerfile fixed.

* docker: use init.sh to setup rust env

polkadot/docker/Dockerfile

@@ -9,11 +9,11 @@ COPY . /polkadot
 
 RUN apt-get update && \
 	apt-get upgrade -y && \
-	apt-get install -y cmake pkg-config libssl-dev git
-
+	apt-get install -y cmake pkg-config libssl-dev git clang
 RUN curl https://sh.rustup.rs -sSf | sh -s -- -y && \
-	export PATH=$PATH:$HOME/.cargo/bin && \
-	cargo build --$PROFILE
+        export PATH=$PATH:$HOME/.cargo/bin && \
+        scripts/init.sh && \
+        cargo build --$PROFILE
 
 # ===== SECOND STAGE ======