Add image with all toolchains installed

rustup/Dockerfile

@@ -23,10 +23,11 @@ RUN apt-get update && \
 #     OPENSSL_INCLUDE_DIR=/usr/local/ssl/include \
 #     OPENSSL_STATIC=1
 
-ARG TOOLCHAIN
-
 # install toolchain
+ARG TOOLCHAIN
 RUN curl https://sh.rustup.rs -sSf | \
     sh -s -- --default-toolchain $TOOLCHAIN -y
-
 ENV PATH=/root/.cargo/bin:$PATH
+
+ARG EXTRA=""
+RUN for name in "$EXTRA"; do rustup install $name; done