Docker MSBuild
I created an image specifically for building legacy ASP.NET code. This is publicly available on Docker hub and GitHub. You may pull it and use it at your own discretion.
https://hub.docker.com/repository/docker/mrjamiebowman/msbuild
How to Use

First, you’ll want to make sure your local Docker daemon is running Windows Containers.
Pulling the image with Docker is very easy…
docker push mrjamiebowman/msbuild
Once you have the image locally, it’s easy to map in your project into the source folder, build, and publish.
docker run --rm -it -v ${PWD}\source:C:\source -v ${PWD}\published:C:\published --name msbuild mrjamiebowman/msbuild
This will literally build and publish whatever source code that is in the source folder and publish it to the published folder.