use os-specific EOL while creating the copyrightHeader for hygiene checks

[kumarharsh]

Right now, the hygiene checks fail on windows machines because the copyrightHeader standard is being by joining an array of strings with a \n, which doesn't work on Windows with it's CRLF line-endings. This PR addresses that by using OS-specific line endings while building the copyrightHeader standard string.

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[kumarharsh]

bad PR, closing