Add a macOS m1 specific build target for seldon client

[rajatvig]

What this PR does / why we need it:

Ship an ARM Seldon CLI binary that can be used for macOS. The build tags are documented here. Adding the -tags dynamic builds the binary on a macOS M1 and works assuming librdkafka has been installed. brew can install it.

Which issue(s) this PR fixes:
None

Special notes for your reviewer:

Unsure how the release for the binary happens and where to add any documentation for it.

[seldondev]

Hi @rajatvig. Thanks for your PR.

I'm waiting for a SeldonIO or todo member to verify that this patch is reasonable to test. If it is, they should reply with /ok-to-test on its own line. Until that is done, I will not automatically test new commits in this PR, but the usual testing commands by org members will still work. Regular contributors should join the org to skip this step.

Once the patch is verified, the new status will be reflected by the ok-to-test label.

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[sakoush]

Many thanks for the contribution @rajatvig
This looks fine. Could you also add a note in the docs to reflect this feature: e.g. in docs/source/contents/getting-started/cli.md and docs/source/contents/cli/index.md?

[rajatvig]

@sakoush Have updated the docs.