Add testing for arm64

**Describe the problem/challenge you have**
Similar to kapp-controller, we should add some kind of testing that verifies the arm64 version of SGC runs properly.

https://github.com/vmware-tanzu/carvel-kapp-controller/issues/736

**Describe the solution you'd like**
[A clear and concise description of what you want to happen. If applicable a visual representation of the UX.]

**Anything else you would like to add:**
[Additional information that will assist in solving the issue.]

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