bug#12714: [PATCH] build: do not redefine _FORTIFY_SOURCE

[Jim Meyering]

Mike Frysinger wrote:
> If the active compiler or flags have already defined _FORTIFY_SOURCE,
> don't go overriding that.  Otherwise we get a lot of spew about the
> flag being redefined.
>
> * configure.ac (FORTIFY_SOURCE): Check if _FORTIFY_SOURCE is defined.
> ---
>  configure.ac | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/configure.ac b/configure.ac
> index e5e05be..6504144 100644
> --- a/configure.ac
> +++ b/configure.ac
> @@ -170,7 +170,7 @@ if test "$gl_gcc_warnings" = yes; then
>    AH_VERBATIM([FORTIFY_SOURCE],
>    [/* Enable compile-time and run-time bounds-checking, and some warnings,
>        without upsetting glibc 2.15+. */
> -   #if defined __OPTIMIZE__ && __OPTIMIZE__
> +   #if !defined _FORTIFY_SOURCE && defined __OPTIMIZE__ && __OPTIMIZE__
>     # define _FORTIFY_SOURCE 2
>     #endif
>    ])

Thanks.  Please adjust the log (or just tell us and we'll adjust it)
so that we know which compiler motivates this change.