RFC: Changing AC_PROG_CC to AC_PROG_CC_C99 in top level configure

[Joseph Myers]

On Mon, 26 Apr 2021, Nick Clifton via Gcc-patches wrote:

> Hi Guys,
> 
>   Given that gcc, gdb and now binutils are all now requiring C99 as a
>   minimum version of C, are there any objections to updating
>   configure.ac to reflect this ?

This isn't an objection, since upgrading auto* for the toolchain can be 
complicated, but note that AC_PROG_CC_C99 is obsolete in Autoconf 2.70 and 
instead AC_PROG_CC enables C11 mode if supported.  (So moving to the 
latest Autoconf and Automake releases would supersede this change.)

-- 
Joseph S. Myers
joseph@codesourcery.com