Dockerfile built-in ARGs

Dockerfile

FROM alpine

ARG TARGETPLATFORM
ARG TARGETOS
ARG TARGETARCH
ARG TARGETVARIANT
ARG BUILDPLATFORM
ARG BUILDOS
ARG BUILDARCH
ARG BUILDVARIANT
RUN echo "Building on $BUILDPLATFORM, targeting $TARGETPLATFORM"
RUN echo "Building on ${BUILDOS} and ${BUILDARCH} with optional variant ${BUILDVARIANT}"
RUN echo "Targeting ${TARGETOS} and ${TARGETARCH} with optional variant ${TARGETVARIANT}"

See: https://docs.docker.com/build/building/multi-platform/