Don't use "-linkobj" when compile for a binary or test

Currently in `compilepkg.go`, when we invoke `go tool compile`, we are unconditionally adding `-linkobj` to create 2 separate artifacts: `.x` for downstream library compilation and `.a` for downstream binary linking.

This is efficient for `go_library`, but for the compilation which happens under `go_test` and `go_binary`, the output artifact(s) will not be used for any other downstream actions except GoLink for that test/binary to create the final Go executable.

So for the GoCompilePkg action under `go_test` and `go_binary`, it will be better if we remove `-linkobj` and only generate the `.a` file. In other words, we should only be using `-linkobj` when the downstream consumer of the artifact is unclear, such as for the GoCompilePkg action under `go_library` or `go_proto_library`.

Start in compilepkg.go and trace how GoCompilePkg is configured for go_test, go_binary, go_library, and go_proto_library, including the go tool compile invocation. Verify which artifacts GoLink consumes; done means test and binary compilations produce only the .a artifact while library and proto-library compilations retain -linkobj behavior.

Written by the indexing model from the issue text.