I get the message: WARNING: readline-style completion disabled due to rl_completion_matches() signature mismatch

The rl_completion_matches test fails due to conflicting options for gcc asking for both for no output and specifying an output file at the same time.

(config.log)
============
Failed: cc -c readline/readline.h -DHAVE_READLINE conftest__.c -o conftest__.o
cc: fatal error: cannot specify -o with -c, -S or -E with multiple files
compilation terminated.
child process exited abnormally
============
The failed code was:

             #include <stdio.h>
             #ifdef HAVE_EDITLINE
             #include <editline/readline.h>
             #else
             #include <readline/readline.h>
             #endif
             static char * rcg(const char *z, int i){(void)z; (void)i; return 0;}
             int main(void) {
               char ** x = rl_completion_matches("one", rcg);
               (void)x;
               return 0;
             }
           
============

If I edit auto.def to remove the test for "rl_completion_matches" the build succeeds and rl_completion_matches works fine in the final executable.