Build armbian with GPT support

[aaditya]

@viumden I had same issue with u-boot from Radxa Debian image (rockpi4-debian-stretch-desktop-arm64-20190730_2022-gpt.img.gz).

However newer u-boot provided here worked and was able to boot:

Index of /rockpi4/images/loader/spi

Reference:

Fail to boot armbian images after spi bootloader upgrade

This is likely that you write an old u-boot-spi image to the SPI, which only support GPT partitions. The Armbian images uses mbr partition. We have added the both mbr and gpt support in the latest u-boot-spi image. https://dl.radxa.com/rockpi4/images/loader/spi/uboot-trust-spi-20190816_1128.img The rockpi4b-rk-u-boot-latest package already contains that. You can hook up a serial console to get the detail of what happened during the boot. https://wiki.radxa.com/Rockpi4/dev/serial-console