Make Dockerfile multiarch.

Support for:
- amd64
- arm64
- armv7
- armv6

docker/Dockerfile

@@ -1,15 +1,13 @@
-FROM frolvlad/alpine-glibc
-
-# Supercronic install settings
-ENV SUPERCRONIC_URL=https://github.com/aptible/supercronic/releases/download/v0.1.8/supercronic-linux-amd64 \
-    SUPERCRONIC=supercronic-linux-amd64 \
-    SUPERCRONIC_SHA1SUM=be43e64c45acd6ec4fce5831e03759c89676a0ea
+FROM gronis/alpine-glibc
 
+RUN ARCH=$(uname -m | sed 's/x86_64/amd64/g' | sed 's/aarch64/arm64/g' | sed 's/armv7l/arm/g') && \
+    SUPERCRONIC_SHA1SUM=$(echo $ARCH | sed 's/amd64/5ddf8ea26b56d4a7ff6faecdd8966610d5cb9d85/g' | sed 's/arm64/e2714c43e7781bf1579c85aa61259245f56dbba1/g' | sed 's/arm/47481c3341bc3a1ae91a728e0cc63c8e6d3791ad/g') && \
+    SUPERCRONIC_URL=https://github.com/aptible/supercronic/releases/download/v0.1.9/supercronic-linux-$ARCH && \
+    SUPERCRONIC=supercronic-linux-$ARCH && \
     # Install SeaweedFS and Supercronic ( for cron job mode )
-# Tried to use curl only (curl -o /tmp/linux_amd64.tar.gz ...), however it turned out that the following tar command failed with "gzip: stdin: not in gzip format"
-RUN apk add --no-cache --virtual build-dependencies --update wget curl ca-certificates && \
-    wget -P /tmp https://github.com/$(curl -s -L https://github.com/chrislusf/seaweedfs/releases/latest | egrep -o 'chrislusf/seaweedfs/releases/download/.*/linux_amd64.tar.gz') && \
-    tar -C /usr/bin/ -xzvf /tmp/linux_amd64.tar.gz && \
+    apk add --no-cache --virtual build-dependencies --update wget curl ca-certificates && \
+    wget -P /tmp https://github.com/$(curl -s -L https://github.com/chrislusf/seaweedfs/releases/latest | egrep -o "chrislusf/seaweedfs/releases/download/.*/linux_$ARCH.tar.gz") && \
+    tar -C /usr/bin/ -xzvf /tmp/linux_$ARCH.tar.gz && \
     curl -fsSLO "$SUPERCRONIC_URL" && \
     echo "${SUPERCRONIC_SHA1SUM}  ${SUPERCRONIC}" | sha1sum -c - && \
     chmod +x "$SUPERCRONIC" && \