Make the script POSIX compliant

[psqli]

There are some cases where Bash is not available or a smaller shell is used to run scripts (e.g. Debian Almquist shell). These changes make the script POSIX compliant, allowing it run in those shells.

• Common bashisms were replaced by POSIX compliant alternatives.
• A fallback for mktemp was added.
• A message was added to inform the user where fnm is being installed.

[changeset-bot]

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Latest commit: b3820ff

Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.

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Project	Deployment	Preview	Comments	Updated (UTC)
fnm	Ready	Preview	Comment	Sep 11, 2025 8:43pm