Enable ARM64 build in CI

[ThomsonTan]

ARM64 build target of opentelemetry-cpp is supported, it will be great if we have CI to track the status of ARM64 build

[github-actions]

This issue was marked as stale due to lack of activity.

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[lalitb]

Copying from discussion - Just a thought, we can at-least add CI to build the otel-cpp for ARM using clang/gcc cross-compiler. Mayn't run the unit-tests as that would need the qemu emulator and could be slow. There are various container offering for ARM cross compiler on x86 containers to use it - https://github.com/dockcross/dockcross. Sort of partial test, but good to investigate.