Ignore .vcxproj files during DocFX build

I'm working with a solution that is a mixed C# - C++/CLI - C++ thing and I'm using DocFX to generate the API docs for the C# project. However, when I build the doc I get a warning ending with "...because the file extension '.vcxproj' is not associated with a language.". I know C++ is not supported but since the C++ stuff is an entirely internal thing does not have be documented anyway. Unfortunately, I cannot seem to be able to make DocFX ignore it using the "exclude" parameters in the .json file.

Anyone else who's come across this situation?

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