Fix:
error: implicitly declaring library function 'exit' with type 'void (int) __attribute__((noreturn))' [-Werror,-Wimplicit-function-declaration]
https://github.com/usnistgov/SCTK/issues/29
--- src/sclite/config.sh.orig	2021-10-28 07:48:48.000000000 -0500
+++ src/sclite/config.sh	2021-11-07 05:56:04.000000000 -0600
@@ -688,6 +688,7 @@
 #line 688 "configure"
 #include "confdefs.h"
 #include <ctype.h>
+#include <stdlib.h>
 #define ISLOWER(c) ('a' <= (c) && (c) <= 'z')
 #define TOUPPER(c) (ISLOWER(c) ? 'A' + ((c) - 'a') : (c))
 #define XOR(e, f) (((e) && !(f)) || (!(e) && (f)))
--- src/asclite/core/config.sh.orig	2021-10-28 07:48:48.000000000 -0500
+++ src/asclite/core/config.sh	2021-11-07 05:56:11.000000000 -0600
@@ -3039,6 +3039,7 @@
 cat >>conftest.$ac_ext <<_ACEOF
 /* end confdefs.h.  */
 #include <ctype.h>
+#include <stdlib.h>
 #if ((' ' & 0x0FF) == 0x020)
 # define ISLOWER(c) ('a' <= (c) && (c) <= 'z')
 # define TOUPPER(c) (ISLOWER(c) ? 'A' + ((c) - 'a') : (c))
--- src/asclite/test/config.sh.orig	2021-10-28 07:48:48.000000000 -0500
+++ src/asclite/test/config.sh	2021-11-07 05:56:33.000000000 -0600
@@ -3039,6 +3039,7 @@
 cat >>conftest.$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))