vsoptions.d should be nothrow

[WalterBright]

[dlang-bot]

Thanks for your pull request, @WalterBright!

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Testing this PR locally

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dub run digger -- build "master + dmd#13960"

[WalterBright]

Blocked by https://github.com/dlang/druntime/pull/3796

[ljmf00]

@WalterBright rebase

[Geod24]

CI points to a lot of things not being nothrow yet.

[RazvanN7]

@WalterBright this is still failing on windows.