yaml-cpp breaks incremental builds

The yaml-cpp subproject should build cleanly and should reach a quiescent build state.

Building the solution always causes yaml-cpp to be rebuilt, which slows down testing in Visual Studio (each time developer hits F5, it always has to first rebuild yaml-cpp).

Start with the yaml-cpp subproject in the Visual Studio solution and reproduce the issue by building the solution twice. Inspect the project’s incremental-build inputs and outputs; done means a subsequent build, including the build before F5, reaches a quiescent state without rebuilding yaml-cpp.

Written by the indexing model from the issue text.