Add a --linux shortcut to --target-os=linux

[robert-ancell]

Description

Improve the Linux build options by making a shortcut for --target-os=linux like the other OS have.

Related Issues

No issue.

Tests

I added the following tests:

No tests added

Checklist

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• I updated/added relevant documentation.
• All existing and new tests are passing.
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Reviewer Checklist

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Breaking Change

Did any tests fail when you ran them? Please read handling breaking changes.

• No, no existing tests failed, so this is not a breaking change.
• Yes, this is a breaking change.