rstan models failing on windows

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We see an error in compilation of just rstan models in our CI with #487 (comment) this flag.

@kcharniga also reports this issue on her new windows machine suggesting it is wider than a CI issue. Kelly did you see the same makevars warning or a different error?

The follow up action here is to test CI with other stan models to see if it is a rstan problem or a rstan with out models problem.

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This last passing CI: https://github.com/epinowcast/epidist/actions/runs/12073118551

and this is the first failing one: https://github.com/epinowcast/epidist/actions/runs/12112515981 not that only windows is failing.

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Here the issue is with rstan for all models tested

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User report: #487 (comment)