Project never up-to-date because of missing designtime.props file

(originally reported in https://marketplace.visualstudio.com/items?itemName=TheQtCompany.QtVisualStudioTools-19123)

"Recently converted a VS2017 with Qt 5.13.1 project to use the latest Qt Vs Tools project settings, but I'm running into an issue with building.

Visual Studio detects a change every time on build rather than saying the project is up to date. I enabled diagnostic logging to identify the change, and it is related to this:

1>Project is not up-to-date: build input '<project>\x64\Debug\qtvars_bbjsqcqv.2xg.designtime.props' is missing.

When I rename the qtvars designtime file that is already there to match what it's expecting, it's fine. But if I do a clean, it generates a new property file and I'm back in the same situation."