Allow running EC2 jobs locally

[JonathanBrouwer]

The command

cargo run --manifest-path src/ci/citool/Cargo.toml run-local dist-x86_64-linux

Fails locally with the error "Only Linux jobs can be executed locally", which I think is not correct.
The os is displayed as ec2-x86_64ami-c8a.8xlarge-x64-linux-$github.run_id-$github.run_attempt.
This was my hack to fix it, but I'm not sure if the problem should be fixed here or whether the os string is wrong

[rustbot]

r? @marcoieni

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The reviewer was selected based on:

• Owners of files modified in this PR: infra-ci
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[Mark-Simulacrum]

I think this is reasonable.

@bors r+ rollup

r? me

[rust-bors]

📌 Commit f11d76f has been approved by Mark-Simulacrum

It is now in the queue for this repository.

🌲 The tree is currently closed for pull requests below priority 10. This pull request will be tested once the tree is reopened.

Reason for tree closure: Main branch is broken