Add Dockerfile override for ARM64

Signed-off-by: Alex Ellis <alexellis2@gmail.com>

auth/basic-auth/Dockerfile.arm64

+FROM golang:1.10-alpine3.9 as build
+
+RUN apk add --no-cache curl ca-certificates gcc musl-dev
+RUN curl -sLSf https://raw.githubusercontent.com/teamserverless/license-check/master/get.sh | sh \
+  && mv ./license-check /usr/bin/
+
+WORKDIR /go/src/handler
+COPY . .
+
+# Run a gofmt and exclude all vendored code.
+
+RUN license-check -path ./ --verbose=false "OpenFaaS Authors" "OpenFaaS Author(s)" \
+ && test -z "$(gofmt -l $(find . -type f -name '*.go' -not -path "./vendor/*"))" \
+ && go test $(go list ./... | grep -v /vendor/) -cover && \
+ CGO_ENABLED=0 GOOS=linux go build --ldflags "-s -w" -a -installsuffix cgo -o handler .
+
+FROM alpine:3.9
+# Add non-root user
+RUN addgroup -S app && adduser -S -g app app \
+    && mkdir -p /home/app \
+    && chown app /home/app
+
+WORKDIR /home/app
+
+COPY --from=build /go/src/handler/handler    .
+
+RUN chown -R app /home/app
+
+USER app
+
+WORKDIR /home/app
+
+CMD ["./handler"]
+

auth/basic-auth/build.sh

@@ -3,11 +3,13 @@ set -e
 
 export arch=$(uname -m)
 export eTAG="latest-dev"
+export DOCKERFILE="Dockerfile"
 
 if [ "$arch" = "armv7l" ] ; then
    eTAG="latest-armhf-dev"
 elif [ "$arch" = "aarch64" ] ; then
    eTAG="latest-arm64-dev"
+   DOCKERFILE="Dockerfile.arm64"
 fi
 
 echo "$1"
@@ -24,4 +26,5 @@ NS=openfaas
 
 echo Building $NS/basic-auth-plugin:$eTAG
 
-docker build -t $NS/basic-auth-plugin:$eTAG .
+docker build -t $NS/basic-auth-plugin:$eTAG . -f $DOCKERFILE
+