What is a Builder Image?
A "builder image" is a Docker image which contains all the necessary components to build a Slice application. Although it requires you to install and become slightly familiar with Docker, it completely eliminates the need to manually install all third-party libraries, compilers, etc. and also makes updates to the latest Slice version trivial, since all you have to do is pull the latest builder image, instead of having to manually install the updated library and header files.
Image Tags
Windows: registry.gitlab.com/rsethc/slice/slice-builder-windows:master
Ubuntu 20.04 "Focal": registry.gitlab.com/rsethc/slice/slice-builder-ubuntu:master
Builder images for other platforms can be added upon request.
Although under normal circumstances you should stick to using the builder image from the master branch, you can use a different name if you're chasing improvements that are actively being developed in other branches, just beware that there is no guarantee whatsoever that any builder image in the container registry for a side branch is stable or complete whatsoever, and by habitually using a builder image from a side branch you risk missing out on features, performance improvements, and stability fixes if the branch is behind master or stops having images being built for it (for example, if the branch stops being updated because it has already been merged into master).
To build your application, use a Dockerfile, starting with FROM (the image tag). Next, after making sure you have set your WORKDIR to /game, COPY in your source code, and RUN the commands to build your application into /game/built. Finally, you'll probably want to RUN a command such as zip or tar to create an archive of /game/built, and retrieve this file in some way, such as uploading it to artifact storage via curl, or on the host, docker copying the archive out of a container temporarily created from the built image.
In the Slice3D Test project, take a look at the builders directory.
Windows is Special
To keep things simple, the Windows builder image is based on Ubuntu rather than a Windows base image. The benefit is that build scripts, etc. can be exclusively written for Linux.