Since update to the VS2019 the solution is continually rebuild. The dependency paths are not constructed correct. I attach a sample solution.
Reproducing steps:

1. Install Qt version 5.12.6
2. Replace include/dependency paths in the solution to the correct path on your machine.
3. Build the solution => you will see following warning:
   C:\Program Files (x86)\Microsoft Visual Studio\2019\Professional\MSBuild\Microsoft\VC\v160\Microsoft.CppCommon.targets(240,5): warning MSB8064: Custom build for item "test_widget.ui" succeeded, but specified dependency "c:\qt_samples\cont_ui_rebuild\my_widgets\mybutton.h" does not exist. This may cause incremental build to work incorrectly.
4. Start application => VS2019 will start to build again already built solution and you will see the same warning.

Reason: The dependency path is built wrong: It should be "c:\qt_samples\my_widgets\mybutton.h" instead of "c:\qt_samples\cont_ui_rebuild\my_widgets\mybutton.h".

I reported this issue first to Microsoft, they assert that this is Qt issue. Here is the link to report:

https://developercommunity.visualstudio.com/t/continual-solution-rebuild/1403452?from=email