1. change some directory structure for the build script

2. add build script and document
   see DOC/BuildVentoyFromSource.txt for detail

GenUUID/vtoy_gen_uuid.c

@@ -0,0 +1,50 @@
+/******************************************************************************
+ * vtoy_gen_uuid.c 
+ *
+ * Copyright (c) 2020, longpanda <admin@ventoy.net>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 3 of the
+ * License, or (at your option) any later version.
+ * 
+ * This program is distributed in the hope that it will be useful, but
+ * WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * General Public License for more details.
+ * 
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <errno.h>
+#include <unistd.h>
+#include <fcntl.h>
+
+int main()
+{
+    int i;
+    int fd;
+    unsigned char uuid[16];
+    
+    fd = open("/dev/random", O_RDONLY);
+    if (fd < 0)
+    {
+        srand(time(NULL));        
+        for (i = 0; i < 16; i++)
+        {
+            uuid[i] = (unsigned char)(rand());
+        }
+    }
+    else
+    {
+        read(fd, uuid, 16);
+    }
+    
+    fwrite(uuid, 1, 16, stdout);
+    return 0;
+}