Fix:

error: implicitly declaring library function 'exit' with type 'void (int) __attribute__((noreturn))' [-Werror,-Wimplicit-function-declaration]
--- configure.orig	2007-01-14 13:44:58.000000000 -0600
+++ configure	2024-08-02 17:52:03.000000000 -0500
@@ -3014,6 +3014,7 @@
 cat >>conftest.$ac_ext <<_ACEOF
 /* end confdefs.h.  */
 #include <ctype.h>
+#include <stdlib.h>
 #if ((' ' & 0x0FF) == 0x020)
 # define ISLOWER(c) ('a' <= (c) && (c) <= 'z')
 # define TOUPPER(c) (ISLOWER(c) ? 'A' + ((c) - 'a') : (c))
@@ -3027,7 +3028,7 @@
 
 #define XOR(e, f) (((e) && !(f)) || (!(e) && (f)))
 int
-main ()
+main (void)
 {
   int i;
   for (i = 0; i < 256; i++)