[MTK] Q版本刷GSI注意事项

[DESCRIPTION]

 Q版本要跑cts-on-gsi和跑VTS的机器刷GSI方式有差异，请参考下表。

 前提条件：

 adb和fastboot需要升级到最新版本，否则执行fastboot reboot fastboot会出现unknown command的错误。

 Google官网最新platform tools下载路径如下：

 https://developer.android.com/studio/releases/platform-tools

[SOLUTION]

For Q new devices:

 For devices from P OTA to Q :

1. Flash MTK user full load
2. Boot to home screen
3. Settings -> System -> Developer options -> OEM unlocking
4. Reboot phone into fastboot mode by "adb reboot bootloader" or "press volume up key + power key"
5. Connect phone to PC and then type following commands
6. fastboot flashing unlock (press volumn up key)

For projects which don't have vbmeta partition, please use following step 7.
7. fastboot flash --disable-verity boot_a boot.img

For projects which have vbmeta partition, please use following step 7.
7. fastboot flash --disable-verity vbmeta vbmeta.img (vbmeta.img is MTK's vbmeta.img. Please get it from MTK load.)

8. fastboot flash system system.img (system.img is GSI.)
9. fastboot reboot

If the project enables A/B update feature, you need to change steps to flash system partition as below.
fastboot flash system_a system.img (system.img is GSI.)
fastboot flash system_b system.img (system.img is GSI.)