Use the deterministic compiler flag for elixir/rabbitmq_cli

[HoloRin]

Proposed Changes

Passes the +deterministic flag to the erlang compiler during elixir compilation. We already use the flag for the rest of the code, so this brings things more in sync.

Note that this only applies to the Bazel build at this point, Make/Erlang.mk are unaffected.

Types of Changes

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• Bug fix (non-breaking change which fixes issue #NNNN)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause an observable behavior change in existing systems)
• Documentation improvements (corrections, new content, etc)
• Cosmetic change (whitespace, formatting, etc)

Checklist

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• I have read the CONTRIBUTING.md document
• I have signed the CA (see https://cla.pivotal.io/sign/rabbitmq)
• I have added tests that prove my fix is effective or that my feature works
• All tests pass locally with my changes
• If relevant, I have added necessary documentation to https://github.com/rabbitmq/rabbitmq-website
• If relevant, I have added this change to the first version(s) in release-notes that I expect to introduce it

Further Comments

I intend to address the Make/Erlang.mk side of this in another PR.