Tier 1 goal: Test Rust natively on Arm with Travis CI

[hug-dev]

Hi All!

I posted my question about this topic on the Rust forum.

In a nutshell, as Travis CI now supports native builds on Arm64, it could be a good opportunity to set up a job on it running Rust CI tests on the aarch64-unknown-linux-gnu target.
If it is possible for Rust CI infrastructure to have both Azure and Travis CI systems and if all tests run successfully on aarch64-unknown-linux-gnu target this could mean the promotion of this target as Tier 1.

Last time I checked, all tests were passing but the variable arguments ones and this is addressed by @parched at rust-lang/rust#62207

[hug-dev]

Moved the discussion on rust-lang/infra-team#34