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

[tritao]

What does this PR do?

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

Did you check all the boxes?

• 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

You can now support Premake on our OpenCollective. Your contributions help us spend more time responding to requests like these!

[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.