Requested changes to multi-arch build

cmd/kured/Dockerfile.multi

@@ -1,9 +1,19 @@
-FROM golang:bullseye AS build
+FROM --platform=$BUILDPLATFORM golang:bullseye AS build
+
+ARG TARGETOS
+ARG TARGETARCH
+ARG TARGETVARIANT
+
+ENV GOOS=$TARGETOS
+ENV GOARCH=$TARGETARCH
+ENV GOVARIANT=$TARGETVARIANT
+
 WORKDIR /src
 COPY . .
 RUN go list -f '{{join .Deps "\n"}}' ./cmd/kured | grep -v /vendor/ | xargs go list -f '{{if not .Standard}}{{ $dep := . }}{{range .GoFiles}}{{$dep.Dir}}/{{.}} {{end}}{{end}}'
-RUN CGO_ENABLED=0 GOOS=linux go build -o cmd/kured/kured cmd/kured/*.go
-FROM alpine:latest as bin
+RUN CGO_ENABLED=0 go build -o cmd/kured/kured cmd/kured/*.go
+
+FROM --platform=$TARGETPLATFORM alpine:3.15 as bin
 RUN apk update --no-cache && apk upgrade --no-cache && apk add --no-cache ca-certificates tzdata
 COPY --from=build /src/cmd/kured/kured /usr/bin/kured
 ENTRYPOINT ["/usr/bin/kured"]