Don't write to the install log file if it's a reparse point or a directory

[Blue (OneBlue)]

Summary of the Pull Request

This change updates the WriteInstallLog() logic to refuse to write the file if it's a reparse point.

PR Checklist

• Closes: Link to issue #xxx
• Communication: I've discussed this with core contributors already. If work hasn't been agreed, this work might be rejected
• Tests: Added/updated if needed and all pass
• Localization: All end user facing strings can be localized
• Dev docs: Added/updated if needed
• Documentation updated: If checked, please file a pull request on our docs repo and link it here: #xxx

Detailed Description of the Pull Request / Additional comments

Validation Steps Performed

[Copilot]

Copilot review overview

🔵 Needs a closer look

Restore the previous read/write/delete sharing flags to avoid breaking log rotation or backup operations.

Review effort: Lite
Findings: None

What changed in this PR

Updates install-log writing to reject reparse points, directories, and hard-linked files before modification.

Changes:

• Adds validated log-writing implementation logic.
• Preserves error suppression in the logging wrapper.
• Adds unit tests for invalid and valid targets.

File	Reviewed changes
test/​windows/​UnitTests.cpp	Tests rejected paths and preserved target contents.
src/​windows/​common/​install.h	Declares the testable implementation helper.
src/​windows/​common/​install.cpp	Validates log targets before writing.

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