When reading the object files for linking, liblink takes care of
generate the data for them.

This is a port of https://golang.org/cl/3101 to Go.

Change-Id: Ie3e2d6515bd7d253a8c1e25c70ef8fed064436d8
Signed-off-by: Shenghou Ma <minux@golang.org>
Reviewed-on: https://go-review.googlesource.com/8383Reviewed-by: Ian Lance Taylor <iant@golang.org>