Add a os.hostarch() function to get the host system architecture.

[tritao]

What does this PR do?

Add a os.hostarch() function to get the host system architecture.

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• Focus on a single fix or feature; remove any unrelated formatting or code changes
• Add unit tests showing fix or feature works; all tests pass
• Mention any related issues (put closes #XXXX in comment to auto-close issue when PR is merged)
• Follow our coding conventions
• Minimize the number of commits
• Align documentation to your changes

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[tritao]

Just realized host_arch does not follow the rest of the conventions, any preference between os.hostarch or os.hostArch as the name?

[samsinsane]

Just realized host_arch does not follow the rest of the conventions, any preference between os.hostarch or os.hostArch as the name?

os.hostarch would be the preferred name.

[tritao]

Updated the PR with fixed naming.

[tritao]

@samsinsane This one should be ready to go, would be great if we can get this one merged since I'd like to send another one that builds on top of this.