[RFC PATCH, binutils] Add support for creating ELF import libraries

[Hans-Peter Nilsson]

> From: "Thomas Preud'homme" <thomas.preudhomme@foss.arm.com>
> Date: Mon, 25 Jan 2016 14:21:20 +0800

> TL;DR: is there interest for generic ELF import libraries (beside ARM)?

+1

(not speaking for the maintainers that can approve this; just
"my users" and as one who has been in contact with
--extract-symbols from the wrong end)

Regarding the implementation I just offer a 2c observation:
I'm on the fence whether this is better implemented *properly*
(not --extract-symbols) in objcopy but probably still requiring
a struct elf_backend_data hook like the one you add, or as you
do, in the linker.  Maybe gold maintainers would prefer the
former.

brgds, H-P