Improve the error message to be more actionable when no input files are provided for autorest tool

This issue often happens specially when users use `copy-apiversion.ps1` to create new api version specs in which there is a bug in creating a new tag.

More contexts: autorest won't seem to make changes on its code. we might see if any improvements can be made in the downstream tools.

**Example PR**
[[Microsoft.App] Label history Delete API and Label History Status by gdhuper · Pull Request #32738 · Azure/azure-rest-api-specs](https://github.com/Azure/azure-rest-api-specs/pull/32738/checks?check_run_id=38331085039)

**Pipeline Run**
[Example run](
https://dev.azure.com/azure-sdk/internal/_build/results?buildId=4625908&view=logs&j=0303ead4-2e3b-557b-303e-fe8735d4d18f&t=b29b24f0-8be9-5e66-edce-54fd3565c09c)