fix warning: implicit declaration of function ‘exit’

client/flash.c

@@ -9,6 +9,7 @@ BOOL UsbConnect(void);
 
 #include <stdio.h>
 #include <string.h>
+#include <stdlib.h>
 #include "flash.h"
 #include "elf.h"
 

client/flasher.c

@@ -1,4 +1,5 @@
 #include <stdio.h>
+#include <stdlib.h>
 #include "proxusb.h"
 #include "flash.h"