Liblink is still needed for the linker (for a bit longer) but mostly not.
Delete the unused parts.

Change-Id: Ie63a7c1520dee52b17425b384943cd16262d36e3
Reviewed-on: https://go-review.googlesource.com/6110Reviewed-by: Rob Pike <r@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>