How does one translate TARGETPLATFORM into aarch64?

[axblum]

Given the following sample dockerfile, how does one translate the builtin ARG TARGETARCH into aarch64 as the artifacts are named using this as the architecture identifier? Ideally, I would be able to build the multiarch image using this command
docker build -f Dockerfile-t test --platform linux/arm64, linux/amd64

FROM amazoncorretto:11
ARG TARGETARCH
ADD ${TARGETARCH} . 

[crazy-max]

You can use https://github.com/tonistiigi/xx for this and xx-info march:

FROM amazoncorretto:11
COPY --from=tonistiigi/xx / /
ARG TARGETPLATFORM
RUN echo march=$(xx-info march)

But you will not be able to use this in ADD I think.

[axblum]

Do you think this would be worth putting in a feature request for? This would simplify a lot of dockerfiles.

[crazy-max]

We discuss about it here: moby/buildkit#4168