The repository is part of the Compiler Explorer project. It builds the docker images used to build some of the more...esoteric...tools used on the site.
For example, it builds the 6502 compiler.
It's in the process of being broken into smaller docker files, and/or separate repos as appropriate.
What "as appropriate" means is stlil being workde on. Each dockerfile is for one group of related
things, building a XXX-builder for the Dockerfile.XXX file. The misc Dockerfile itself is
for the super misc-y things that really only are one-off, though that's still being split up.
If you add a new Dockerfile, you'll need to edit the matrix in the .github/workflows/build.yml file.
Note: make sure you chmod +x build/build-yourcompiler.sh first
docker build -t builder -f Dockerfile.misc .
docker run --rm -v/tmp/out:/build builder ./build-yourcompiler.sh trunk /build
docker run -t -i miscbuilder bash./build-yourcompiler.sh trunk