Add Alpine Dockerfile

docker/Dockerfile

@@ -0,0 +1,28 @@
+FROM alpine:3.7
+
+RUN set -ex && \
+  addgroup -S miner && \
+  adduser -S -D -h /xmrig -G miner miner && \
+  apk --no-cache upgrade && \
+  apk --no-cache add \
+    libuv \
+    libmicrohttpd && \
+  apk --no-cache add --virtual .build-deps \
+    git \
+    cmake \
+    libuv-dev \
+    libmicrohttpd-dev \
+    build-base && \
+  cd xmrig && \
+  git clone https://github.com/xmrig/xmrig build && \
+  cd build && \
+  cmake -DCMAKE_BUILD_TYPE=Release . && \
+  make && \
+  cd .. && \
+  cp build/xmrig /usr/bin && \
+  rm -rf build && \
+  apk del .build-deps || return 0
+
+USER miner
+WORKDIR /xmrig
+ENTRYPOINT ["/usr/bin/xmrig"]