Weird failure when building with GCC 15 in the default -std=gnu23 mode

[michel-slm]

rlwrap fails to build in Fedora's mass rebuild for the upcoming Fedora 42: https://bugzilla.redhat.com/show_bug.cgi?id=2341282

The error is curious:

readline.c: In function ‘message_in_echo_area’:
readline.c:192:5: error: too many arguments to function ‘rl_message’; expected 0, have 1
  192 |     rl_message(message);
      |     ^~~~~~~~~~ ~~~~~~~
In file included from rlwrap.h:189,
                 from readline.c:23:
/usr/include/readline/readline.h:410:12: note: declared here
  410 | extern int rl_message ();
      |            ^~~~~~~~~~

But readline in Fedora has not been upgraded (the previous successful build is also against readline 8.2).

Compiling with an override to build with -std=gnu17 works around the issue (GCC now defaults to -std=gnu23 per https://gcc.gnu.org/gcc-15/porting_to.html)

I've not managed to figure out what's going on yet, I figured I'll work around it first but report it here, since this will eventually affect more distributions too as GCC 15 adoption spreads.