[RFA] Add --enable-codesign to gdb's configure

[Joel Brobecker]

Hi Tom,

On Thu, Jun 28, 2018 at 10:37:45AM -0600, Tom Tromey wrote:
> macOS requires that the gdb executable be signed in order to be able
> to successfully use ptrace.  This must be done after each link.
> 
> This patch adds a new --enable-codesign configure option so that this
> step can be automated.
> 
> gdb/ChangeLog
> 2018-06-28  Tom Tromey  <tom@tromey.com>
> 
> 	* NEWS: Mention --enable-codesign.
> 	* silent-rules.mk (ECHO_SIGN): New variable.
> 	* configure.ac: Add --enable-codesign.
> 	* configure: Rebuild.
> 	* Makefile.in (CODESIGN, CODESIGN_CERT): New variables.
> 	(gdb$(EXEEXT)): Optionally invoke codesign.

Good idea! The NEWS portion needs to wait for Eli's feedback.
But the rest looks good to me (the NEWS entry too, FWIW).

Thank you!
-- 
Joel