The answer to your first beef is that it would complicate the specification unnecessarily. You would suddenly have to provide a lot more details in the language

The answer to your first beef is that it would complicate the specification unnecessarily. You would suddenly have to provide a lot more details in the language spec, such as defining what capabilities a filesystem must provide, environment variables, OS and architecture details, package formats, compiler invocation syntax, and so on. That's all taken care of by the go tool right now, and doesn't burden other compiler implementations with all that. Expediency is not used as a justification for this at all. You're wrong that any compiler control flags get involved here; 6g is going to be invoked with exactly the same syntax, and doesn't get told anything about "internal", just as it isn't told anything about build tags, or OS/arch-specific filename control (e.g. foo_linux.go).