Following this tutorial, if I remove the installPath and use the default MsBuild Visual Studio location, I get the following error.
Error: Visual Studio Build Tools 2019 (2) is already installed
I built a similar container a few weeks back and everything worked, however something appears to have moved and I'm unable to work out what.
Adding the modify parameter to the vs_BuildTools.exe command resolves this issue. Unfortunately it forces an installPath to be included but can be set to the default location.