Try to fix doc build on docs.rs

[Coloquinte]

This is an attempt to fix the issue I opened for docs.rs build.

I kept it simple and just disabled the build of the C/C++ libraries when the doc is built.

Building the doc works locally, but I couldn't confirm it works on docs.rs.

[chrjabs]

Thanks for this easy fix. I was aware of the problem but didn't have the time to think of a solution yet.