hi there, first up - warnings are just that, warnings, and they generally don’t make your build crash (which is indeed what happened here - your site built, right?)
can you pop a screenshot of your build settings and also of your netlify.toml please?
Yup, that warning message is confusing and we have an issue filed to get it addressed. Do let us know if your site is not building correctly as a result, please (I think you said it is not?)