Explore buildah in place of kaniko

[matifali]

https://buildah.io/

Buildah is an OCI image builder by the same team who builds podman. It's worth exploring if we can get any benefits using buildah in place of kaniko.

[aaronlehmann]

We just migrated from using envbuilder directly to processing .devcontainer with envbuilder's devcontainer.Compile and invoking buildah with the resulting Dockerfile, env, etc. (also embedding buildah in our Go code). The big win for us is ability to prepull and unpack base images in advance so they are ready to go when running the actual build. This base image pulling and unpacking can dominate the build time with kaniko. Also, buildah uses overlayfs when available, so snapshotting is free and more robust than kaniko's userspace mechanism.