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

[Gabriel F. T. Gomes]

On Tue, 18 Dec 2018, Joseph Myers wrote:

>In the NEWS entry, the requirement for a newer GCC version for
>powerpc64le is reiterated (as in the entry for the 4.9 requirement in
>2.26) to avoid suggesting the version requirement there has gone down.

Thanks for writing this.

>Tested for x86_64.

On powerpc64le, it still complains that GCC 5 is not enough, as expected.

>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.

Looks good to me.