Issue when trying to build multi platform image

[WeihanLi]

When I try to build a multi-platform image following the instructions on the blog post https://devblogs.microsoft.com/dotnet/improving-multiplatform-container-support/

Failed to build on the arm platform, the Dockerfile is as follows:

FROM  --platform=$BUILDPLATFORM mcr.microsoft.com/dotnet/runtime:9.0-preview-alpine AS base
LABEL Maintainer="WeihanLi"

FROM mcr.microsoft.com/dotnet/sdk:9.0-preview-alpine AS build-env
ARG TARGETARCH
WORKDIR /app
COPY ./src/ ./src/
COPY ./build/ ./build/
COPY ./Directory.Build.props ./
COPY ./Directory.Build.targets ./
COPY ./Directory.Packages.props ./
WORKDIR /app/src/dotnet-exec/
ENV HUSKY=0
RUN dotnet publish -f net9.0 -a $TARGETARCH -o /app/artifacts

FROM base AS final
WORKDIR /app
COPY --from=build-env /app/artifacts/ ./
ENV PATH="/app:${PATH}"
RUN chmod +x ./dotnet-exec
ENTRYPOINT [ "dotnet-exec" ]
CMD [ "--help" ]

failed CI: https://github.com/WeihanLi/dotnet-exec/actions/runs/8044724737/job/21968771547

works when only built for linux/amd64, failed when enabling the arm platform, is there more config I missed?

WeihanLi/dotnet-exec@91450ce

full project here: https://github.com/WeihanLi/dotnet-exec/tree/91450ce2cc6f8429830762a3833af2f6cce891db

[WeihanLi]

Ah, found it, should add --platform=$BUILDPLATFORM for the sdk image, the failure is using --platform=$BUILDPLATFORM for the runtime image