Fix clang version

golang/latest/Dockerfile

@@ -11,11 +11,11 @@ RUN go get -u golang.org/x/lint/golint
 
 # Install clang
 RUN apt-get update && apt-get install -y --no-install-recommends \
-    clang \
+    clang-5.0 \
     && apt-get clean \
     && rm -rf /var/lib/apt/lists/* /tmp/* /var/tmp/*
 
 # Set Clang as default CC
 ENV set_clang /etc/profile.d/set-clang-cc.sh
 SHELL ["/bin/bash", "-o", "pipefail", "-c"]
-RUN echo "export CC=clang-7.0" | tee -a ${set_clang} && chmod a+x ${set_clang}
+RUN echo "export CC=clang-5.0" | tee -a ${set_clang} && chmod a+x ${set_clang}