Signed-off-by: Avi Deitcher avi@deitcher.net

- What I did

In PR #3650 we moved the logic for calculating the hash for an arch-specific alpine image from inside tools/alpine/Makefile to inside tools/alpine/Dockerfile and then consumed it. This was a good idea, but the implementation had two issues:

• The actual usage of TARGETARCH did so in a way that left it as a literal ${TARGETARCH} rather than interpolated correctly by the Dockerfile
• The file was named /etc/alpine-hash, which implied that it was the generic, multi-arch index, when really it is just the arch-specific one

This PR corrects both of the above. It ensures that TARGETARCH is interpolated by the Dockerfile, and it saves the file as /etc/alpine-hash-arch.

This does not resolve the question of having an alpine image carry the multi-arch tag, likely in /etc/alpine-hash, as that is a more complicated issue, and something we never had before (one step up). Instead, it just fixes a regression from #3650 so that this all works correctly.

If I can figure out a sane way to get /etc/alpine-hash before this PR goes in, I will update this PR, else it will be the subject of a separate one (potentially).

- How I did it

Modified tools/alpine/Makefile and tools/alpine./Dockerfile

- How to verify it

CI is your friend. Also, you can do what I did, which is to build linuxkit/alpine manually on different platforms and check the content of /etc/alpine-hash-arch.

- Description for the changelog

Fix alpine hash file generation