support arm for shibboleth-idp

[jakelandis]

Work in progress.

diff from fork: jakelandis/shibboleth-idp-dockerized@7f8b92b...master

To test on arm device

1. update the platform (I will clean up how we build the image)
2. ./gradlew :x-pack:qa:saml-idp-tests:javaRestTest --info

Note - I think we have some outstanding clean up issues with these running containers, so it might fail if not starting from a clean slate. Just run again (or manually clean up the running docker instances).

Also note ... building from a linux base image instead of the upstream image i forked since we will eventually want to update/upgrade and the upstream image appears to no longer be getting updates.

[jakelandis]

change here to test arm

[mark-vieira]

This worked for me after a changed a couple of things:

1. First I had to pass linux/arm64/v8 as the --platform
2. I had to change the condition on TARGETARCH to check for arm64 instead of arm64v8.

I think we don't actually have to worry about (1). Passing --platform should actually only be necessary when overriding the default, which is to use the host platform. Second, I think we might have to change the TARGETARCH stuff anyway, as that is coming from buildx and I don't think we want to rely on that. As I mentioned before, we don't have to worry about multi-arch images here, we'll just build for the host platform and by default, Docker already handles this transparently. The only thing we need to handle explicitly is downloading any architecture-specific binaries within the Dockerfile, which in our case is just the JDK. That said, we could simplify that even further by just using a base image with a JDK already installed, like one of the official openjdk images, which are already multi-arch. That way we don't deal with architecture at all, and when the image is built locally, it automatically targest the host architecture.

[jakelandis]

Thanks Mark ! These pointers make sense and will work on adopting these.

[jakelandis]

superseded by: #91216