Add multi platforms support for RepoOutDir

[TrevorTaoARM]

Add multi-platform output dir support for
arm64 and other platforms, which is used in
archive, package(deb, rpm), docker
build actions.

Signed-off-by: TrevorTaoARM trevor.tao@arm.com

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[istio-testing]

Hi @TrevorTaoARM. Thanks for your PR.

I'm waiting for a istio 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.

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[howardjohn]

I am fine doing this short term but I think for Istio official builds we would probably only be doing both ARM and AMD at once, so we may need more work there in that regard

[howardjohn]

Actually this would mean that users on non-linux/amd64 can no longer build a proper release. For example, someone running on OSX now gets a osx build which is not what we want. The build platform != target platform IMO

[ericvn]

Doing some testing with MacOS as John mentioned, but running into another issue that I need to fix first :(.