Currently the bots are pulling VS 2017 via gclient to build the Windows engine. This means that errors building with VS 2019, which is what most people would now install, go undetected; currently there are at least some type conversion issues in ANGLE that are causing build errors with 2019 but not 2017.

We should switch to pulling 2019. That change should be straightforward, but we need to fix the build errors first.