how to build Stock Android Oreo 8.1 from source code for rock64？

[frankwz]

i build the Android source 8.1,but not succcess boot from sd card,anybody know why ??
i just want to run the sdcard boot image for rock64 board by build it myself by http://files.pine64.org/os/sdk/ROCK64/RO...8.1.tar.gz source code.
rock64 img from (http://wiki.pine64.org/index.php/ROCK64_...d_8.x_eMMC) this is ok,
but why myself build is not work

any guy know why?
how  should i do , or change something?

I have a rock64  board(mem  1g),and i have download the ROCK64 Android Oreo ver8.1 SDK from link http://files.pine64.org/os/sdk/ROCK64/RO...8.1.tar.gz.
i have setup the android build environment for ubuntu16.04.1 LTS desktop,and build the source success
source build.sh

and i get the image in rockdev/Image-rk3328_box
vps@ubuntu:~/rk3328v81_box$ uname -r
4.15.0-39-generic
vps@ubuntu:~/rk3328v81_box$ uname -a
Linux ubuntu 4.15.0-39-generic #42~16.04.1-Ubuntu SMP Wed Oct 24 17:09:54 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux
vps@ubuntu:~/rk3328v81_box$ ls -al rockdev/Image-rk3328_box/
total 2727264
drwxrwxr-x 2 vps vps       4096 Nov 23 07:49 .
drwxrwxr-x 3 vps vps       4096 Nov 23 07:47 ..
-rwxrwxr-x 1 vps vps    1048576 May 15  2018 baseparameter.img
-rw-rw-r-- 1 vps vps    1491516 Nov 23 07:47 boot.img
-rw-rw-r-- 1 vps vps   18970644 Nov 23 02:44 kernel.img
-rw-rw-r-- 1 vps vps     162126 Nov 23 02:31 MiniLoaderAll.bin
-rwxrwxr-x 1 vps vps      49152 May 15  2018 misc.img
-rw-rw-r-- 1 vps vps     168060 Nov 23 07:49 oem.img
-rwxrwxr-x 1 vps vps        981 May 15  2018 parameter.txt
-rw-rw-r-- 1 vps vps      49152 May 15  2018 pcba_small_misc.img
-rw-rw-r-- 1 vps vps      49152 May 15  2018 pcba_whole_misc.img
-rw-rw-r-- 1 vps vps    9260688 Nov 23 07:47 recovery.img
-rw-rw-r-- 1 vps vps      95232 Nov 23 02:50 resource.img
-rw-rw-r-- 1 vps vps 1201701108 Nov 23 07:48 system.img
-rw-rw-r-- 1 vps vps    4194304 Nov 23 02:31 trust.img
-rw-rw-r-- 1 vps vps    4194304 Nov 23 02:31 uboot.img
-rw-rw-r-- 1 vps vps 1396378072 Nov 23 07:49 update.img
-rw-rw-r-- 1 vps vps  154861692 Nov 23 07:49 vendor.img

but when i flash the update.img to sd card,
Win32DiskImager or SD_Firmware_Tool.

the board could note boot success!