Apply best practices to Dockerfile

Dockerfile

 # Build Geth in a stock Go builder container
 FROM golang:1.17-alpine as builder
 
-RUN apk add --no-cache make gcc musl-dev linux-headers git bash
+RUN set -x \
+	&& buildDeps='bash build-base musl-dev linux-headers git' \
+	&& apk add --update $buildDeps \
+	&& rm -rf /var/cache/apk/* \
+    && mkdir -p /bor
 
-ADD . /bor
-RUN cd /bor && make bor-all
+WORKDIR /bor
+COPY . .
+RUN make bor-all
 
 CMD ["/bin/bash"]
 
 # Pull Bor into a second stage deploy alpine container
-FROM alpine:latest
+FROM alpine:3.14
+
+RUN set -x \
+    && apk add --update --no-cache \
+       ca-certificates \
+    && rm -rf /var/cache/apk/*
 
-RUN apk add --no-cache ca-certificates
 COPY --from=builder /bor/build/bin/bor /usr/local/bin/
 COPY --from=builder /bor/build/bin/bootnode /usr/local/bin/
 
-EXPOSE 8545 8546 8547 30303 30303/udp
\ No newline at end of file
+EXPOSE 8545 8546 8547 30303 30303/udp