Fix:
error: implicitly declaring library function 'exit' with type 'void (int) __attribute__((noreturn))' [-Werror,-Wimplicit-function-declaration]
https://github.com/egallesio/STklos/commit/9fb3d90d171190a06feb79695b2ad3664a231ee6
--- configure.orig	2021-11-24 07:45:28.000000000 -0600
+++ configure	2023-03-12 11:14:33.000000000 -0500
@@ -7222,8 +7222,8 @@
 else $as_nop
   cat confdefs.h - <<_ACEOF >conftest.$ac_ext
 /* end confdefs.h.  */
- void inner (char *foo) { char bar; exit (!(foo >= &bar)); }
-             void main () { char foo; inner (&foo); }
+ int inner (char *foo) { char bar; return !(foo >= &bar); }
+             int main (void) { char foo; return inner (&foo); }
 _ACEOF
 if ac_fn_c_try_run "$LINENO"
 then :
