Require GCC 5 or later to build glibc (bug 23993)

[Carlos O'Donell]

On 12/18/18 1:45 PM, Florian Weimer wrote:
> * Joseph Myers:
> 
>> 2018-12-18  Joseph Myers  <joseph@codesourcery.com>
>>
>> 	[BZ #23993]
>> 	* configure.ac (libc_cv_compiler_ok): Require GCC 5 or later.
>> 	* configure: Regenerated.
>> 	* manual/install.texi (Tools for Compilation): Update minimum GCC
>> 	version.
>> 	* INSTALL: Regenerated.
> 
> Patch looks okay to me.
> 
> However, can we keep support/ at a GCC 4.9 level for some time?  This
> will simplify backporting to glibc 2.27 and 2.28.  I expect to backport
> regularly to these branches for about a year, maybe longer, particularly
> for glibc 2.28.

I don't object.

You are the defacto support/ subsystem maintainer, and because we want
support/ to be rebased to various branches to improve testing coverage
I think it's reasonable to request that support/ be slightly more
restrictive (restricts what features can be used) for a subset of gcc
versions e.g. continue to support gcc 4.9.

-- 
Cheers,
Carlos.