str(1): without <sysexits.h> fall back to ANSI C

src/str.c

@@ -20,9 +20,10 @@
 #include <ctype.h>
 #include <stddef.h> /* NULL */
 #include <stdio.h> /* fprintf(3) */
+#include <stdlib.h> /* EXIT_FAILURE */
 #include <string.h> /* strcmp(3) */
 #if !defined EX_USAGE
-#	include <sysexits.h>
+#	define EX_USAGE EXIT_FAILURE
 #endif
 
 static char *program_name = "str";