generate_config_includefile should display an error if no files are found at all

[jphickey]

Is your feature request related to a problem? Please describe.
While testing other items I noticed that the generate_config_includefile function will happily create an empty file if neither a user-provided file nor a default/fallback file is available.

But because the file is present but doesn't have any actual content, you end up with a slightly obfuscated compiler error about missing symbols rather than an indication that the expected config file is empty.

Describe the solution you'd like
The function should trigger an error and inform the user that there was no file to use, rather than generating an empty file. It is a misconfiguration, so it should be corrected.

Requester Info
Joseph Hickey, Vantage Systems, Inc.

[jphickey]

Calling it an "enhancement" as it isn't strictly broken - more of a reporting/informational concern. Could be argued to be a bug though, as the build should inform the user if their config is broken.