Fix & improve install.sh

[clairem-sl]

Description

1. Fix the chopped error message
2. Make color escape sequence adapt to $TERM
3. Add NOBACKUP option

Related Issues

• Enhances Linux: Wrapper and scripts modernizations #4982 ; my changes don't conflict with the changes there

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Checklist

Please ensure the following before requesting review:

• I have provided a clear title and detailed description for this pull request.
• If useful, I have included media such as screenshots and video to show off my changes.
• The PR is linked to a relevant issue with sufficient context.
• I have tested the changes locally and verified they work as intended.
• All new and existing tests pass.
• Code follows the project's style guidelines.
• Documentation has been updated if needed.
• Any dependent changes have been merged and published in downstream modules
• I have reviewed the contributing guidelines.

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Additional Notes

To invoke the NOBACKUP option, just specify the word as an argument to the install script. For example:

# Non-root installation
./install.sh NOBACKUP

# Root installation
sudo ./install.sh NOBACKUP

[github-actions]

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[clairem-sl]

I have read the CLA Document and I hereby sign the CLA

[akleshchev]

Shouldn't this aim at a linux branch?

[DarlCat]

Hey @clairem-sl; in the interest of helping this along could you please retarget this towards the develop-linux branch to help the Lindens out when they're able to begin their review? 😄

It's possible at the top of the pull request, by clicking edit, then underneath the title you should see a dropdown for the target branch open up so you can swap it over.

As for the why, it's the branch where a large chunk of the Linux work is currently centered around before it is merged into the develop branch proper, so it doesn't make a lot of sense to target the upstream develop branch before the Linux work itself is merged there.