missing spl/u-boot-spl-ddr.bin when building Uboot for Coral

Hi I am trying to build Uboot for the Google Coral board.

I did the following on my Ubuntu 20.04 laptop:

sudo apt install g++-aarch64-linux-gnu
sudo apt install device-tree-compiler

git clone https://coral.googlesource.com/uboot-imx
make ARCH=arm64 mx8mq_phanbell_defconfig
make CROSS_COMPILE=aarch64-linux-gnu- u-boot.imx

I am getting an error message at the end of the build and it says something like Can't open spl/u-boot-spl-ddr.bin.

Anyone has a clue what is going on? Thank you so much.