fix: Adding platform check before invoking dllimport method

[nickrandolph]

GitHub Issue (If applicable): related to unoplatform/uno#15635

PR Type

What kind of change does this PR introduce?

• Bugfix

What is the current behavior?

Dllimported method GetCurrentPackageFullName is invoked on all platforms other than WASM. It should only be invoked on Windows

What is the new behavior?

Platform check ensures GetCurrentPackageFullName is only called on Windows

PR Checklist

Please check if your PR fulfills the following requirements:

• Tested code with current supported SDKs
• Docs have been added/updated which fit documentation template. (for bug fixes / features)
• Unit Tests and/or UI Tests for the changes have been added (for bug fixes / features) (if applicable)
• Wasm UI Tests are not showing unexpected any differences. Validate PR Screenshots Compare Test Run results.
• Contains NO breaking changes
• Updated the Release Notes
• Associated with an issue (GitHub or internal)

Other information

Internal Issue (If applicable):