Updated Dockerfile for cross-build.

Dockerfile

@@ -1,13 +1,14 @@
-FROM golang:latest AS pitemp-builder
+FROM golang:alpine AS pitemp-builder
 
 # Builder image
 WORKDIR /pitemp
 COPY . .
-RUN go build
+RUN GOOS="linux" GOARCH=$(uname -m | sed -e "s/aarch64/arm64/" -e "s/x86_64/amd64/" -e "s/armv7l/arm/") go build
 
 # Final image
-FROM debian:stable-slim
-RUN apt-get update && apt-get install --yes ca-certificates
+FROM alpine:latest
+RUN apk --no-cache add ca-certificates
+#RUN apt-get update && apt-get install --yes ca-certificates
 COPY --from=pitemp-builder /pitemp/pitemp /usr/local/bin/pitemp
 ENTRYPOINT ["/usr/local/bin/pitemp"]
 CMD ["--help"]