The final stage is scratch, which has no C library, but the builder
compiled mfer with cgo on (the golang image's default). The binary
imports net (mfer's own HTTP code does, and so does google/uuid), so
with cgo on it came out dynamically linked and the image could not
start. The image's go build now sets CGO_ENABLED=0; nothing in mfer
needs cgo. A new builder step runs ldd on the binary and fails the
build unless it reports a static executable.
Model: opus-5-5