Fix:

error: implicitly declaring library function 'exit' with type 'void (int) __attribute__((noreturn))' [-Werror,-Wimplicit-function-declaration]

Based on:

https://src.fedoraproject.org/rpms/t1lib/blob/rawhide/f/t1lib-configure-c99.patch
--- configure.orig	2007-12-23 09:49:43.000000000 -0600
+++ configure	2024-06-14 16:06:22.000000000 -0500
@@ -2888,7 +2888,7 @@
   echo "$as_me:$LINENO: \$? = $ac_status" >&5
   (exit $ac_status); }; }; then
   for ac_declaration in \
-   '' \
+   '#include <stdlib.h>' \
    'extern "C" void std::exit (int) throw (); using std::exit;' \
    'extern "C" void std::exit (int); using std::exit;' \
    'extern "C" void exit (int) throw ();' \
@@ -5787,8 +5787,8 @@
   for (i = 0; i < 256; i++)
     if (XOR (islower (i), ISLOWER (i))
 	|| toupper (i) != TOUPPER (i))
-      exit(2);
-  exit (0);
+      return 2;
+  return 0;
 }
 _ACEOF
 rm -f conftest$ac_exeext
@@ -6291,7 +6291,7 @@
   fi
 fi
 for ac_declaration in \
-   '' \
+   '#include <stdlib.h>' \
    'extern "C" void std::exit (int) throw (); using std::exit;' \
    'extern "C" void std::exit (int); using std::exit;' \
    'extern "C" void exit (int) throw ();' \
@@ -10322,10 +10322,6 @@
 #  endif
 #endif
 
-#ifdef __cplusplus
-extern "C" void exit (int);
-#endif
-
 void fnord() { int i=42;}
 int main ()
 {
@@ -10339,7 +10335,7 @@
       /* dlclose (self); */
     }
 
-    exit (status);
+    return status;
 }
 EOF
   if { (eval echo "$as_me:$LINENO: \"$ac_link\"") >&5
@@ -10420,10 +10416,6 @@
 #  endif
 #endif
 
-#ifdef __cplusplus
-extern "C" void exit (int);
-#endif
-
 void fnord() { int i=42;}
 int main ()
 {
@@ -10437,7 +10429,7 @@
       /* dlclose (self); */
     }
 
-    exit (status);
+    return status;
 }
 EOF
   if { (eval echo "$as_me:$LINENO: \"$ac_link\"") >&5
@@ -14038,10 +14030,6 @@
 #  endif
 #endif
 
-#ifdef __cplusplus
-extern "C" void exit (int);
-#endif
-
 void fnord() { int i=42;}
 int main ()
 {
@@ -14055,7 +14043,7 @@
       /* dlclose (self); */
     }
 
-    exit (status);
+    return status;
 }
 EOF
   if { (eval echo "$as_me:$LINENO: \"$ac_link\"") >&5
@@ -14136,10 +14124,6 @@
 #  endif
 #endif
 
-#ifdef __cplusplus
-extern "C" void exit (int);
-#endif
-
 void fnord() { int i=42;}
 int main ()
 {
@@ -14153,7 +14137,7 @@
       /* dlclose (self); */
     }
 
-    exit (status);
+    return status;
 }
 EOF
   if { (eval echo "$as_me:$LINENO: \"$ac_link\"") >&5
@@ -19560,10 +19544,6 @@
 #  endif
 #endif
 
-#ifdef __cplusplus
-extern "C" void exit (int);
-#endif
-
 void fnord() { int i=42;}
 int main ()
 {
@@ -19577,7 +19557,7 @@
       /* dlclose (self); */
     }
 
-    exit (status);
+    return status;
 }
 EOF
   if { (eval echo "$as_me:$LINENO: \"$ac_link\"") >&5
@@ -19658,10 +19638,6 @@
 #  endif
 #endif
 
-#ifdef __cplusplus
-extern "C" void exit (int);
-#endif
-
 void fnord() { int i=42;}
 int main ()
 {
@@ -19675,7 +19651,7 @@
       /* dlclose (self); */
     }
 
-    exit (status);
+    return status;
 }
 EOF
   if { (eval echo "$as_me:$LINENO: \"$ac_link\"") >&5
@@ -24526,7 +24502,7 @@
   unsigned int B = 3;
   int i;
   for(i=0; i<B; i++) Array[i] = i - 3;
-  exit( Array[1] != -2 );
+  return Array[1] != -2;
 }
 _ACEOF
 rm -f conftest$ac_exeext