When Emacs has unsaved changes for a file foo.go, it creates an intentionally broken symbolic link .#foo.go. (See "Protection against Simultaneous Editing" or "Why does emacs create temporary symbolic links for modified files?".)

go/build gracefully ignores these, because it has ignored files starting with . or _ since its very first import.

cmd/dist complains about them though, because it breaks the bootstrap copying process. This prevents running make.bash while Emacs has unsaved changes to toolchain source files.