Add Dockerfile

By default this Dockerfile is suitable for using dockerhub auto build
feature to build new :latest when ever there's a new push to the
github master branch allowing for simple "official" image
distribution.

Adding build args allow specifying alternate repository (default:
https://github.com/xmrig/xmrig.git) or build reference (default:
master) example:

docker build --build-arg repo=https://github.com/<username>/xmrig.git \
             --build-arg ref=dev --tag xmrig:dev .

A multi stage build is used to keep run time image small.

Dockerfile

@@ -0,0 +1,45 @@
+# Build in disposable container so run-time container is small
+FROM alpine:latest as build
+
+# Build from master by default but allow build time specification
+ARG ref=master
+ENV my_ref=$ref
+
+# Developers may wish to specify an alternate repository for source
+ARG repo=https://github.com/xmrig/xmrig.git
+ENV my_repo=$repo
+
+RUN set -ex && \
+        # testing required for hwloc
+	echo @testing http://nl.alpinelinux.org/alpine/edge/testing >> /etc/apk/repositories
+
+RUN set -ex && \
+	apk --no-cache --update add \
+	    coreutils file grep openssl tar binutils \
+	    cmake g++ git linux-headers libpthread-stubs make hwloc-dev@testing \
+	    libuv-dev openssl-dev
+
+WORKDIR /usr/local/src
+
+RUN set -ex && \
+    	git clone $my_repo xmrig && \
+	cd xmrig && git checkout $my_ref && \
+	cmake -B build && \
+	cd build && \
+	make 
+
+# runtime container
+FROM alpine:latest
+
+RUN set -ex && \
+        # testing required for hwloc
+	echo @testing http://nl.alpinelinux.org/alpine/edge/testing >> /etc/apk/repositories
+
+RUN set -ex && \
+	apk --no-cache --update add \
+	# required libraries packages
+		openssl libuv hwloc@testing
+
+COPY --from=build /usr/local/src/xmrig/build/xmrig /bin/
+
+ENTRYPOINT ["/bin/xmrig"]