CI with Glibc-2.23, Clang-4.0 (#683)

.maintain/docker/Dockerfile.aarch64-linux-gnu

@@ -21,9 +21,9 @@ FROM rustembedded/cross:aarch64-unknown-linux-gnu
 # only for aarch64
 
 # change mirrorlist
-RUN apt update && apt upgrade -y && apt install -y \
-	# lib
-	libc6-dev-i386 \
-	# compiler
-	gcc-aarch64-linux-gnu gcc-5-aarch64-linux-gnu g++-aarch64-linux-gnu g++-5-aarch64-linux-gnu \
-	clang llvm libclang-dev
+RUN apt update && apt install -y \
+    # lib
+    libc6-dev-i386 \
+    # compiler
+    gcc-aarch64-linux-gnu gcc-5-aarch64-linux-gnu g++-aarch64-linux-gnu g++-5-aarch64-linux-gnu \
+    clang llvm libclang-dev

.maintain/docker/Dockerfile.darwinia.x86_64-linux-gnu

@@ -1,5 +1,5 @@
 FROM debian:stable-slim
-RUN apt-get update && apt-get install -y --no-install-recommends openssl && rm -rf /var/lib/apt/lists/*
+RUN apt update && apt install -y --no-install-recommends openssl && rm -rf /var/lib/apt/lists/*
 COPY deploy/darwinia /usr/local/bin/darwinia
 EXPOSE 30333 9933 9944
 ENTRYPOINT [ "/usr/local/bin/darwinia" ]

.maintain/docker/Dockerfile.x86_64-linux-gnu

@@ -16,13 +16,13 @@
 # You should have received a copy of the GNU General Public License
 # along with Darwinia. If not, see <https://www.gnu.org/licenses/>.
 
-FROM centos:7
+FROM ubuntu:16.04
 
 # for gernal linux
 
 # change mirrorlist
-RUN yum -y update && yum -y upgrade && yum -y install \
-	# tool
-	git make \
-	# compiler
-	clang gcc gcc-c++ llvm
+RUN apt update && apt install -y \
+    # tool
+    git make \
+    # compiler
+    gcc g++ clang-4.0

CHANGELOG.md

@@ -33,7 +33,7 @@
 #### Binary
 |               |  Arch  | glibc (at least) | llvm (at least) | pre-built |
 | :-----------: | :----: | :--------------: | :-------------: | :-------: |
-| General Linux | x86_64 |       2.17       |       3.8       |     ✔︎     |
+| General Linux | x86_64 |       2.23       |       4.0       |     ✔︎     |
 
 #### Docker
 ```docker