Recently I found out that you can have multiple images in a Dockerfile. I found this really helpful for fuzzing, where I could build the harness in one docker image, and then copy only the harness to the AFL++ image. Here is a bit of a bare bone extract of my Dockerfile.
FROM --platform=linux/aarch64 debian AS builder
# rest of the builder stuff
FROM --platform=linux/aarch64 aflplusplus/aflplusplus:latest
COPY --from=builder /build/harness /src/
COPY --from=builder /build/other_stuff_for_fuzzing /src/This is useful, when we only care about the last stage.