Allow kube-bench to be run inside its distribution container

Dockerfile

-FROM golang:1.9
-WORKDIR /kube-bench
-RUN go get github.com/aquasecurity/kube-bench
+FROM golang:1.9 AS build
+WORKDIR /go/src/github.com/aquasecurity/kube-bench/
+ADD glide.lock glide.yaml ./
+RUN go get github.com/Masterminds/glide && glide install
+ADD main.go .
+ADD check/ check/
+ADD cmd/ cmd/
+RUN CGO_ENABLED=0 go install -a -ldflags '-w'
 
-FROM alpine:latest
-WORKDIR /
-COPY --from=0 /go/bin/kube-bench /kube-bench 
-COPY --from=0 /go/src/github.com/aquasecurity/kube-bench/cfg /cfg
-COPY --from=0 /go/src/github.com/aquasecurity/kube-bench/entrypoint.sh /entrypoint.sh
-ENTRYPOINT /entrypoint.sh
+FROM alpine:latest AS run
+WORKDIR /opt/kube-bench/
+# add GNU ps for -C, -o cmd, and --no-headers support
+# https://github.com/aquasecurity/kube-bench/issues/109
+RUN apk --no-cache add procps
+COPY --from=build /go/bin/kube-bench /usr/local/bin/kube-bench
+ADD entrypoint.sh .
+ADD cfg/ cfg/
+ENTRYPOINT ["./entrypoint.sh"]
 
 # Build-time metadata as defined at http://label-schema.org
 ARG BUILD_DATE