Make the AppVeyor shell script stop on error
Make the AppVeyor shell script stop on error

(Currently it *should* be failing on generateprojects.sh, but it's
not)

iantalarico/google-cloud-dotnet,googleapis/google-cloud-dotnet,evildour/google-cloud-dotnet,evildour/google-cloud-dotnet,googleapis/google-cloud-dotnet,iantalarico/google-cloud-dotnet,jskeet/google-cloud-dotnet,iantalarico/google-cloud-dotnet,jskeet/google-cloud-dotnet,jskeet/google-cloud-dotnet,evildour/google-cloud-dotnet,jskeet/gcloud-dotnet,jskeet/google-cloud-dotnet,jskeet/google-cloud-dotnet,googleapis/google-cloud-dotnet